Wa `alaykum as-salamu wa rahmatullahi wa barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Thank you for your good question and concern about your fellow Muslims.
Sacrificing an animal for Allah’s sake in udhiyyah is a form of showing thanks and gratitude to Allah Almighty, who created us, and gave us life and many blessings. Animals are created by Allah Almighty for certain purposes, among which is to be mercifully slaughtered by humans for food and other acceptable benefits.
Responding to your question, Imam Dr. Wael Shihab, PhD in Islamic Studies from Al-Azhar University, and currently the Imam of the Downtown Toronto Masjid in Canada, sates,
Udhiyyah, a sacrificial animal that is slaughtered in worship of Allah on the day of `Eid Al-Adha, is a confirmed Sunnah according to the majority of Muslim jurists. Abu Hanifah and other scholars regard it as obligatory. A Muslim who is financially able to afford it is highly encouraged to offer it to feed the poor, his family and relatives, and his own self. Only camels, cattle, sheep, or goats may be slaughtered. At the youngest, camels must be over five full years of age, cattle and goats over two full years, and sheep over one full year.
A single camel or cow fulfills the Sunnah for seven men and their families, though a goat or a sheep only fulfills it for one. It is recommended that a third of the animal sacrificed be eaten, a third be gifted to relatives and friends, and a third be given as charity. (See The Kuwaiti Encyclopedia of Jurisprudence, vol. 5, pp 74-107)
Legality and merits of the udhiyyah are evidenced by the Qur’an and the Sunnah. For instance, Allah Almighty says in the Qur’an, (Pray unto they Lord, and sacrifice) (Al-Kawthar 108:2)
This verse means a Muslim should pray `Eid Al-Adha and then sacrifice his udhiyyah for Allah’s sake. Al-Bara’ reported, “I heard the Prophet (peace and blessings be upon him) delivering a khutbah (sermon) saying, “The first thing to be done on this (`Eid Al-Adha) day is to pray; and after returning from the prayer we slaughter our sacrifices (in the name of Allah) and whoever does so, he acted according to our Sunnah.’” (Al-Bukhari)
Historically, udhiyyah has been legislated, as a Sunnah, in the second year after Hijrah, the same year in which `Eid Prayers and zakah were prescribed.
Udhiyyah, in fact, is meant to show gratitude and thankfulness to Allah for His countless blessings and favors. Also, it helps in feeding the poor, the needy, and one’s family and relatives. So, it has religious, social, and economical fruits.
Moreover, udhiyyah revives the Sunnah of Prophet Ibrahim (peace be upon him) when Allah Almighty commanded him to slaughter an animal in ransom for his child, Isma`il (peace be upon him) on the day of Nahr (the day of `Eid Al-Adha). So, udhiyyah is traced back to Prophet Ibrahim (peace be upon him), not a Hindu tradition as the question states.
It is noteworthy that Allah Almighty created people, animals, birds, and everything in the world; He, Most High, created animals for people’s benefits and allowed merciful and kind slaughtering of animals for food.
He, Almighty, says, (And the cattle has He created, whence you have warm clothing and uses, and whereof you eat. And wherein is beauty for you, when you bring them home, and when you take them out to pasture. And they bear your loads for you unto a land you could not reach save with great trouble to yourselves. Lo! Your Lord is Full of Pity, Merciful.) (An-Nahl 16: 5-7)
Given the above, it becomes evident that udhiyyah is a Sunnah that was first practiced by Prophet Ibrahim (peace be upon him) at the command of Allah. It has significant religious, social, and economic objectives.
May Allah Almighty strengthen your faith and ours and guide us all to what is best in this world and the world to come.
Allah Almighty knows best.