Because Allah the Exalted has said in Surah Al-Hajj: "We have made the sacrificial animals among the symbols of Allah for you; there is good for you in them. So mention the name of Allah over them as they are lined up, and when they fall on their sides (i.e., are slaughtered), then eat from them and feed the patient needy and the beggar—both types of poor. Thus We have made these animals lawful for you so that you may be grateful. Neither their meat nor their blood reaches Allah, but what reaches Him is your piety. Thus He has subjected them to you so that you may magnify Allah for what He has guided you to, and give glad tidings to the doers of good." Mujahid said that the sacrificial animal is called «بدنه» because of its fatness; «قانع» refers to the beggar, and «معتر» is one who comes before the sacrificial animal in the form of a beggar, whether he is rich or poor. The meaning of «شعائر» is to consider the greatness of the sacrificial animal and to make it fat. «عتيق» (refers to the Ka'bah) because it is free from oppressors and tyrants. When something falls to the ground, it is said «وجبت» , and from this comes «وجبت الشمس‏» , meaning the sun has set.

Narrated Abu Huraira': Allah's Apostle (p.b.u.h) saw a man driving his Badana (sacrificial camel). He said, "Ride on it." The man said, "It is a Badana." The Prophet said, "Ride on it." He (the man) said, "It is a Badana." The Prophet said, "Ride on it." And on the second or the third time he (the Prophet) added, "Woe to you."

Narrated Anas: The Prophet saw a man driving a Badana. He said, "Ride on it." The man replied, "It is a Badana." The Prophet said (again), "Ride on it." He (the man) said, "It is a Badana." The Prophet said thrice, "Ride on it."

Narrated Ibn `Umar: During the last Hajj (Hajj-al-Wada`) of Allah's Apostle he performed `Umra and Hajj. He drove a Hadi along with him from Dhul-Hulaifa. Allah's Apostle started by assuming Ihram for `Umra and Hajj. And the people, too, performed the `Umra and Hajj along with the Prophet. Some of them brought the Hadi and drove it along with them, while the others did not. So, when the Prophet arrived at Mecca. he said to the people, "Whoever among you has driven the Hadi, should not finish his Ihram till he completes his Hajj. And whoever among you has not (driven) the Hadi with him, should perform Tawaf of the Ka`ba and the Tawaf between Safa and Marwa, then cut short his hair and finish his Ihram, and should later assume Ihram for Hajj; but he must offer a Hadi (sacrifice); and if anyone cannot afford a Hadi, he should fast for three days during the Hajj and seven days when he returns home. The Prophet performed Tawaf of the Ka`ba on his arrival (at Mecca); he touched the (Black Stone) corner first of all and then did Ramal (fast walking with moving of the shoulders) during the first three rounds round the Ka`ba, and during the last four rounds he walked. After finishing Tawaf of the Ka`ba, he offered a two rak`at prayer at Maqam Ibrahim, and after finishing the prayer he went to Safa and Marwa and performed seven rounds of Tawaf between them and did not do any deed forbidden because of Ihram, till he finished all the ceremonies of his Hajj and sacrificed his Hadi on the day of Nahr (10th day of Dhul-Hijja). He then hastened onwards (to Mecca) and performed Tawaf of the Ka`ba and then everything that was forbidden because of Ihram became permissible. Those who took and drove the Hadi with them did the same as Allah's Apostle did.

Narrated 'Urwa: " 'Aishah informed me about the Hajj and 'Umra (together) of the Prophet (saws) and so did the people who were with him (during the Hajj and 'Umra) and narration similar to the narration of the Ibn 'Umar (previous hadith)

Narrated Nafi`: `Abdullah (bin `Abdullah) bin `Umar said to his father, "Stay here, for I am afraid that it (affliction between Ibn Zubair and Al-Hajjaj) might prevent you from reaching the Ka`ba." Ibn `Umar said, "(In this case) I would do the same as Allah's Apostle did, and Allah has said, 'Verily, in Allah's Apostle, you have a good example (to follow).' So, I make you, people, witness that I have made `Umra compulsory for me." So he assumed lhram for `Umra. Then he went out and when he reached Al- Baida', he assumed Ihram for Hajj and `Umra (together) and said, "The conditions (requisites) of Hajj and `Umra are the same." He, then brought a Hadi from Qudaid. Then he arrived (at Mecca) and performed Tawaf (between Safa and Marwa) once for both Hajj and `Umra and did not finish the lhram till he had finished both Hajj and `Umra.

And Nafi‘ said that ‘Abdullah bin ‘Umar (may Allah be pleased with them) when he would take the sacrificial animal with him from Madinah, he would garland it at Dhu’l-Hulayfah and mark it in such a way that when the camel was sitting facing the Qiblah, he would pierce its right hump with a spear.

Narrated Al-Miswar bin Makhrama and Marwan: The Prophet set out from Medina with over one thousand of his companions (at the time of the Treaty of Hudaibiya) and when they reached Dhul-Hulaifa, the Prophet garlanded his Hadi and marked it and assumed Ihram for `Umra.

Narrated Al-Miswar bin Makhrama and Marwan: The Prophet set out from Medina with over one thousand of his companions (at the time of the Treaty of Hudaibiya) and when they reached Dhul-Hulaifa, the Prophet garlanded his Hadi and marked it and assumed Ihram for `Umra.

Narrated `Aisha: I twisted with my own hands the garlands for the Budn of the Prophet who garlanded and marked them, and then made them proceed to Mecca; Yet no permissible thing was regarded as illegal for him then.