Imam al-Bayhaqi رحمه الله relates that Imam ash-Shaafi'ee رحمه الله said:
"Allah سبحانه و تعالى has praised the Companions رضي الله عنهم of the Messenger of Allah صلى الله عليه وسلم in the Qur'aan, the Tawraat (Torah), and the Injeel (the Book given to Prophet Jesus عليه السلام), and their virtue has been established for them upon the tongue of the Messenger of Allah صلى الله عليه وسلم in a way that none after them can receive.
So Allah سبحانه و تعالى has bestowed Mercy upon them, and He has given them good news of the far reaching lofty positions He has given them - the ranks of the truthful ones, the martyrs and the righteous.
They brought us the traditions of the Messenger of Allah صلى الله عليه وسلم, witnessing him whilst the Revelation descended upon him. So they knew what the Messenger of Allah صلى الله عليه وسلم intended, which statements were general and which were specific, which commands were resolute and which were encouraging instructions. They knew everything from his Sunnah that we know, as well as things that we do not know. They are above us in every type of knowledge and verdict, and in piety and intelligence, and in precise points of keen understanding and deduction. And with us their opinions are more praiseworthy and take precedence over the opinions we hold for ourselves, and Allah knows best."
And Imam al-Bayhaqi رحمه الله relates from Muhammad Ibn 'Abdillah Ibn 'Abdil-Hakam رحمه الله who said,
"I heard Imam ash-Shaafi'ee رحمه الله saying, 'The most virtuous of the people after the Messenger of Allah صلى الله عليه وسلم is Abu Bakr, then Umar, then Uthman, then Ali, may Allah be pleased with all of them.'"
"It is from the Sunnah to mention the good qualities of the Companions رضي الله عنهم of the Messenger of Allah صلى الله عليه وسلم, all of them without exception; and to refrain from mentioning the negative things and the differing that occured between some of them. So whosoever insults even one of the Companions رضي الله عنهم of the Messenger of Allah صلى الله عليه وسلم, then such a person is an innovator, a filthy, bankrupt Raafidee (Shi'a). Allaah سبحانه و تعالى will not accept even one of his deeds."
"Loving all of the Companions رضي الله عنهم of the Prophet صلى الله عليه وسلم is Sunnah, supplicating for them is a good deed that brings one close (to Allaah), following their example is a means (to success), and embracing their ways of guidance is a virtue."
"And the Companions رضي الله عنهم of the Messenger of Allah صلى الله عليه وسلم - after the four (Caliphs) رضي الله عنهم - are the best of the people, and it is not permissible for anyone to mention any of their faults, nor to speak ill of any of them, blaming them for deficiencies and shortcomings. It is indeed obligatory upon the ruler to reprimand and punish whoever does that, and he should not be pardoned."
And Ibnul-Jawzee رحمه الله mentiones a letter sent by Imam Ahmad رحمه الله to Musaddad رحمه الله, and it is written therein,
"And (from correct beliefs) is to testify that ten (of the Companions) will be in Paradise (as promised during their lifetimes): Abu Bakr, 'Umar, 'Uthman, 'Ali, Talhah, az-Zubayr, Sa'd, Sa'eed, 'Abdur Rahman Ibn 'Awf, and Abu 'Ubaydah Ibnul-Jarrah رضي الله عنهم. And whoever the Prophet صلى الله عليه وسلم testified for (that he will be in Paradise), we testify that he will be in Paradise."
Imam Al-Ḥasan ibn ʻAlī al-Barbahārī رحمه الله said,
"From the Sunnah is clinging to the Jama'ah. Whoever desires other than the Jama'ah and departs from it, then he has thrown off the yoke of Islaam from his neck and he is astray, leading others astray.
The foundation upon which the Jama'ah is built is the Companions رضي الله عنهم of Muhammad صلى الله عليه وسلم. May Allaah's Mercy be upon them all. They are Ahlus Sunnah wal-Jama'ah , so whoever does not take from them has gone astray and innovated, and every innovation is misguidance, and misguidance and its people are in the Fire. 
So he who contradicts the Companions رضي الله عنهم of Allaah's Messenger صلى الله عليه وسلم in any of the affairs of the Religion, then he has fallen into disbelief."  
1 - Sayyiduna 'Abdullaah Ibn 'Amr رضي الله عنهما reports that the Prophet صلى الله عليه وسلم said, "The Children of Israa'eel split into seventy two sects, and my Ummah will split into seventy three sects, all of them are in the Fire, except one." The Companions asked, "Which one is that, O Messenger of Allaah?" He replied, "That which I and my Companions are upon." Reported by at-Tirmidhee (2641), and declared Saheeh by Shaykh al-Albani رحمه الله
Abu Shamah رحمه الله (d.665H) said, "The order to stick to the Jama'ah means sticking to the truth and its followers; even if those who stick to the truth are few and those who oppose it are many, since the truth is that which the first Jama'ah from the time of the Prophet صلى الله عليه وسلم and his Companions رضي الله عنهم were upon. No attention is given to the great number of the people of futility coming after them." al-Baa'ith 'alal-Bid'ah wal-Hawaadith
2 - Sayyiduna Jaabir رضي الله عنه reports that the Prophet صلى الله عليه وسلم said, "...The most truthful speech is the Book of Allaah. The best way is the way of Muhammad. The worst of affairs are the novelties, and every novelty is a bid'ah (innovation), and ever bid'ah is misguidance and every misguidance is in the Fire." Reported by an-Nisaa'ee (3/188), declared Saheeh by Shaykh al-Albani رحمه الله
Sayyiduna al-'Irbaad Ibn Saariyah رضي الله عنه reports that the Prophet صلى الله عليه وسلم said, "...I have left you upon clear guidance, its night is like its day. No one deviates from it after me except that he is destroyed." Reported by Ahmad, Ibn Majah (43) and al-Haakim. Declared Saheeh by Shaykh al-Albani رحمه الله
3 - Allaah سبحانه و تعالى says:
"And whoever opposes the Messenger after guidance has become clear to him and follows other than the way of the believers - We shall keep him in the path he has chosen, and burn him in Hell - what an evil destination."(4:115)
So whoever abandons their way and instead follows the devils, like the extreme Shi'a, then he has left Islaam.
Imam Al-Ḥasan ibn ʻAlī al-Barbahārī رحمه الله said,
"And the best of this Ummah after its Prophet صلى الله عليه وسلم is Abu Bakr as-Siddeeq, then 'Umar Ibn al-Khattaab, then 'Uthmaan Ibn 'Affaan رضي الله عنهم. We give precedence to these three, just as the Companions of the Messenger of Allaah gave precedence to them. They [the Companions رضي الله عنهم] never differed in that.
Then after those three, the five Companions of the shoora: 'Ali Ibn Abi Taalib, az-Zubayr, Talhah, 'Abdur Rahmaan Ibn 'Awf and Sa'd Ibn Abi Waqqaas رضي الله عنهم. Each of them was fitting and appropriate for Khilaafah, and each of them was an Imaam (leader). In this regard we take the hadeeth of Ibn 'Umar رضي الله عنهما, 'We used to consider, while the Messenger of Allaah صلى الله عليه وسلم was alive and his Companions widespread: Abu Bakr [to be first], then 'Umar, then 'Uthmaan - and then we remained quiet." 
Then after the five Companions of the shoora are the people who fought in the battle of Badr from among the Muhajireen رضي الله عنهم. And then those who fought in the battle of Badr from among the Ansaar رضي الله عنهم. Each one's rank is acording to his migration and precedence (in the Religion).
Then the most superior of makind after these are the rest of the Companions رضي الله عنهم of the Messenger of Allaah صلى الله عليه وسلم. Everyone who accompanied him, whether for a year, a month, a day, an hour or (just merely) saw him, then he is from among his Companions رضي الله عنهم. His companionship is according to the extent to which he accompanied him, [and the extent to which] he had precedence in being with him, heard from him and looked at him.
So the closest to the Messenger of Allaah صلى الله عليه وسلم in companionship to him are more excellent than the generation which did not see, even if they met Allaah with all the [good] actions. Despite that, those who accompanied the Prophet, saw him and heard from his are superior. And whoever saw him with his eyes, and believed in him, even if for just an hour, is more excellent on account of this companionship with the Prophet صلى الله عليه وسلم than the Tabi'een رحمة الله عليهم, even if they (the Tabi'een) did every action of goodness." 
 Reported by al-Bukhari, #3655, Kitab Fada'il as-Sahabah, Chapter: The excellence of Abu Bakr رضي الله عنه after the Prophet صلى الله عليه وسلم. Imam Ahmad رحمه الله in his Musnad (2/14); Ibn Abi Aasim (552); Ibn Katheer رحمه الله narrated something similar in al-Bidayah (7/206 and 12/345) from the narrations of al-Bazzar رحمه الله and said: "And this chain of narration is Saheeh according to the conditions of the Shaykhayn (Imam al-Bukhari رحمه الله and Imam Muslim رحمه الله)." Shaykh al-Albani رحمه الله declared its chain of narration Saheeh, see as-Sunnah li Ibn Abi Aasim (1195). Ahmad Shaakir رحمه الله said: "Its chain of narration is Saheeh," in his Tahqeeq of Musnad Ahmad (4642). Shaykh al-Islam Ibn Taymiyyah رحمه الله said: "Whoever criticises the Khilaafah of any of these A'immah is more astray than his family's donkey." (Majmoo' al-Fataawa 3/153).
Imam Al-Ḥasan ibn ʻAlī al-Barbahārī رحمه الله said,
"Know that anyone who tries to attack any of the Companions رضي الله عنهم of Muhammad صلى الله عليه وسلم really seeks to attack the Prophet صلى الله عليه وسلم and they have caused him harm in his grave."
"My Companions are safety for my Ummah, so when my Companions die, that which my Ummah is promised will come to pass." 
Imam al-Qurtubi رحمه الله comments on this hadeeth, "The meaning of this narration is that: As long as the Prophet's صلى الله عليه وسلم Companions رضي الله عنهم are alive, the religion will be visibly established, truth will be apparent, and victory against the enemies of the religion will take place. When his Companions رضي الله عنهم passed away, the people of desires dominated, and the enemies were given the upper hand. The level of the religion has continued to decrease, and its diligence has recoiled, until eventually there will not remain on the face of the earth anyone saying, 'Allaah, Allaah.' This is that which the Prophet's صلى الله عليه وسلم Ummah has been promised. And Allaah knows best." 
al-Imam an-Nawawi رحمه الله said, "The Companions رضي الله عنهم are a safety from the appearance of innovation, newely invented matters, and trials in the religion, and from the appearance of the horn of the devil, and dominance of Rome and other nations upon them. They were a safety from the attack against al-Madeenah and Makkah and other than that. All of this is from the Prophet's صلى الله عليه وسلم miracles." 
Sayyiduna Hudhayfah رضي الله عنه said, "There is not a long period of time that stands between evil befalling you all except the death of a man, and he is 'Umar." 
Sayyiduna Samra Ibn Jundub رضي الله عنه said, "Verily Islaam was a well fortified fortress, and they have certainly punctured an opening in al-Islaam with the killing of 'Uthman." 
 al-Mufhim 6/485
 Sharh Saheeh Muslim 16/68
 Ibn Abi Shaybah 14/65 #38286, ar-Ruyani 3/107 and Nu'aym Ibn Hamad 1/42. Its chain is authentic.
"So if they believe in the same as you believe in, then they have been [rightly] guided; but if they turn away, they are only in dissension, and Allah will be sufficient for you against them. And He is the Hearing, the Knowing." (2:137)
Mufti Muhammad Shafi رحمه الله writes,
"From the beginning of the Surah Al-Baqarah upto this place, different verses have been explaining the nature and essence of 'Iman (faith), sometimes succinctly and sometimes in detail. Verse 137 defines 'Iman in a simple and short phrase which is at the same time so comprehensive that all possible details and explanations are inherent in it. The earlier verses having established that the only religion which is valid at present is Islam, this verse assures the Muslims that the Jews and the Christians can find the guidance only "if they believe just as you believe", or, in other words, "if they believe in what you believe in." The immediate addressees of the phrase "you believe" are the Holy Prophet صلى الله عليه وسلم and his blessed Companions رضي الله عنهم.
Thus, in doctrinal matters above all, their 'Iman has been placed before us as a model, and the verse is essentially a divine commandment, laying down the fundamental principle that the only 'Iman acceptable to Allah سبحانه و تعالى is the one which was adopted by the Holy Prophet صلى الله عليه وسلم and his blessed Companions رضي الله عنهم, and that any doctrines or beliefs that deviate from it in the least are neither valid nor acceptable to Allaah سبحانه و تعالى. That is to say, one should believe in Allah and His attributes, in the angels, in the Books of Allah, in the messengers and prophets of Allah and in their teachings exactly in the same manner as the Holy Prophet صلى الله عليه وسلم and the blessed Companions رضي الله عنهم did, without adding or substracting anything on one's own part and without advancing one's own interpretations or distorting the authentic meanings of the doctrines. Nor is one allowed to assign to the angels or the prophets a station higher or lower than the one assigned to them by the word or deed of the Holy Prophet صلى الله عليه وسلم. Moreover, one is also required to be sincere and pure in one's faith, for the contrary would amount to hypocrisy (Nifaq).
This cannot be undone and I am sure it will be greatly appreciated.
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