Because Allah the Exalted has said in Surah Al-Hijr: "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."