Shaykh Saalih al-Fawzaan حفظه الله said,
"People are divided into three categories regarding knowledge and deeds: The first category
is represented in those who combine useful knowledge along with righteous deeds. Those are the ones whom Allaah سبحانه و تعالى has guided to the straight path; the path of those upon whom Allaah سبحانه و تعالى has bestowed favour, of the prophets, the steadfast affirmers of truth, the martyrs and the righteous, and excellent indeed are these as companions. The second category
is represented in those who learn useful knowledge but do not act accordingly. Those are the ones who have evoked Allaah's سبحانه و تعالى anger, like the Jews and whoever follows their footsteps. The third category
is represented in those who act without having knowledge. Those are the ones who are astray, namely the Christians and their likes.
These three categories are mentioned in Sooratul-Faatihah (the Opening Chapter of the Qur'aan), which we recite in every rak'ah
(unit of prayer) of our prayers: 'Guide us to the straight path - the path of those upon whom You have bestowed favour, not of those who have evoked [Your] anger or of those who are astray.'
In his interpretation of the aforesaid verses of Sooratul-Faatihah, Shaykhul-Islaam Muhammad Ibn 'Abdil-Wahhaab رحمه الله stated: 'The scholars meant in the verse that reads, "those who have evoked (Allaah's) anger"
are those who do not act in accordance with their knowledge, and "...those who are astray,"
are the ones who act without knowledge. The former is the quality of the Jews, while the latter is that of the Christians. Some ignorant people mistakenly believe that those two qualities are restricted to the Jews and the Christians, forgetting that Allaah سبحانه و تعالى commands them to recite the above-mentioned Qur'anic invocation seeking refuge with Him from being one of the people of these two qualities. Glory be to Allaah! How do those ignorant people think that they are safe from these qualities, though they are taught and commanded by Allaah سبحانه و تعالى to keep on invoking Him (through the aforesaid verses) seeking His refuge against them?! Are they not aware that they thus assume evil about Allaah?!' 
This shows the wisdom behind the obligation of reciting this great Soorah (i.e., Al-Faatihah) in every rak'ah
of our prayers (whether obligatory or supererogatory). It is because this Soorah contains many great secrets, among them is the great Qur'anic invocation that reads, 'Guide us to the straight path - the path of those upon whom You have bestowed favour, not of those who have evoked [Your] anger or of those who are astray.'
(Sooratul-Faatihah, 1:6-7) Through this invocation, we ask Allaah سبحانه و تعالى to guide us to follow the conduct and the way of the people who have useful knowledge and perform righteous deeds, which is the way to salvation in both this world and the Hereafter. We also invoke Him to safeguard us from the pathway of the ones astray, who have neglected either the righteous deeds or the useful knowledge."  Notes:
 Ibn Ghannaam رحمه الله, Taareekh Najd.
 Shaykh Saalih al-Fawzaan حفظه الله, A Summary of Islamic Jurisprudence (Al-Maiman Publishing House), vol. 1, pp. 3-4.
See also: Virtues of Knowledge which is Learnt and Taught for the sake of Allah