Muslims generally celebrate two main festivals of happiness a year, the days of which are known as ‘Eid. The one thing these two festivals have in common is that they always follow a period of worship.
For example, Eid-ul-Fitr comes after the ninth month of the Islamic calendar, known as Ramadan. As we know, Ramadan is a month of discipline and is all about stopping ourselves from bad deeds.
Similarly, Muslims are trained to perform different acts of worship during the last month of the lunar calendar, known as Dhu al-Hijja, from the beginning of the month until the 9th and 10th days.
The Prophet Muhammad (P.B.U.H) said,
"There are no days where in which Allah Almighty loves the act of worship more than the first ten days of Dhu al-Hijja “Sunan Ibn Majah 1727."

What is Eid-Ul-Azha?

According to Muslims, Eid-Ul-Azha is the day of sacrifice or the ‘Eid of sacrifice. Allah Almighty put Prophet Ibrahim (A.S) to the test by questioning if he could sacrifice his son Prophet Ismail (A.S) for me. After that point, Ibrahim (A.S) discussed it with Prophet Ismail (A.S), and he replied,
“O my dear father! Do as you are commanded. Allah willing, you will find me steadfast.” (As-Safat-37:102).”
According to Islamic tradition, when Ibrahim (A.S) was about to sacrifice his son on the instruction of Allah Almighty, Allah replaced the son with a sacrificial animal. Every year, on Eid-Ul-Azha, Muslims commemorate the willingness to sacrifice animals for the sake of Allah.

The Relation between Umrah and Eid-Ul-Azha

Although Umrah and Eid-Ul-Azha are two distinct acts of worship, they are somehow linked.
So, what is Umrah in Islam? It is a Muslim pilgrimage to the holy city of Makkah in Saudi Arabia. Since certain acts of worship are carried out during the Umrah. However, the main focus of Umrah is tawaf, or circumambulating the Kaaba seven times.
The link between Umrah and the rounds between Safa and Marwah now refers to the tale of Hazrat Hājar (A.S). When Prophet Ibrahim (A.S) left his wife and infant son Prophet Ismail (A.S) in the desert by Allah's command, Hazrat Hājar (A.S) rushed seven times between Safa and Marwah in search of water for her and her thirsty infant; Prophet Ismail (A.S).
Moreover, Allah tested Prophet Ibrahim (A.S) and his family many times, yet they always stayed faithful. The incident of leaving Hazrat Hājar and Prophet Ismail (A.S) in the desert tested their trust and reliance on Allah’s plan. As Hazrat Ibrahim showed unshakable faith and obedience to Allah when told to sacrifice his son Prophet Ismail (A.S).
Animals that Can Be Sacrificed on Eid-Ul-Azha
The animals that can be sacrificed or slaughtered on Eid-Ul-Azha are male and female cows, goats, camels, buffaloes, and sheep. To know about the animal and whether it is eligible for sacrifice, some conditions for each type of animal are also given.
Age of the Animal
For checking the age of the eligible animal for sacrifice, here are some basic guidelines:
• Sheep and goats should be a minimum of one year old for sacrifice on Eid-Ul-Azha.
• Cows and buffalos should be at least two years old for sacrifice on Eid-Ul-Azha.
• Camels should be a minimum of five years old for sacrifice on Eid-Ul-Azha.
So, these limitations or conditions on the age of animals are given for a reason. The actual reason is that the animal should be mature enough to be sacrificed. Moreover, these conditions may vary slightly from area to area, but the overall basics stay the same in all Islamic traditions.
Physical Standards of Animals
The sacrifice of the animal is required to be devoid of all faults.
• They must not be blind, one-eyed, or have lost more than one-third of their sight.
• They cannot have lost or been born with a third (or more) of their ear or tail.
• Their horn(s) cannot be separated from the root.
• They must not have a lame leg that is so feeble that they cannot walk on it.
• They must not be overly skinny.
• They must be able to walk themselves to the abattoir.
• They cannot be toothless or have more than half of their teeth missing.
These standards are set to ensure that the animal that is going to be slaughtered for Allah should be free from all defects and major physical problems. By following these standards, Muslims make sure to sacrifice the perfect animal in the name of Allah.
Why Hens or Chickens can’t be Slaughtered on Eid-Ul-Azha?
One of the Muslims’ most frequently asked queries about Eid-Ul-Azha is why it is not permitted to sacrifice hens or chicks on Eid-Ul-Azha. So, if we look at the lives of the Prophet Muhammad (PBUH) and his companions, we can find that only four animals were sacrificed on Eid-Ul-Azha. Which are, irrespective of gender, camel, cow, sheep, and goat.
The meat of these four animals is considered better in Islam than all other halal options such as chicken, fish, etc. This is because of the several health benefits linked with the meat of these animals.
If we explore Islamic festivals and their ways of celebration in depth, we will discover that whenever Allah commanded us to celebrate something, it was said to slay a goat, a camel, or a sheep. For example, "Aqeeqa" is an Islamic occasion involving a sacrifice after the birth of a child, and it is recommended to sacrifice sheep or goats.

Bottom Line
Islam is a complete way of life and every teaching of Islam is for the ultimate benefit of human beings. From the view of dietary benefits, we can confirm from the modern medical sciences that the meat of cows, camels, goats, and sheep is the healthiest and better option due to several unique features. That is why Allah wants us to eat the meat from these four animals.
On the other hand, it also fulfills another basic purpose of Eid-Ul-Azha, which is sharing meat with others. According to Islam, three meat parts should be prepared: one for relatives, one for neighbors, and one for the needy.
"Neither their meat nor blood reaches Allah. Rather, it is your piety that reaches Him. This is how He has subjected them to you so that you may proclaim the greatness of Allah for what He has guided you to, and give good news to the good-doers" Al-Hajj 37.”
It indicates that Allah doesn't need the meat or blood of the sacrificed animal from us, but it is actually for our greatest advantage.