In the Guide, Maimonides talks about the religion of the Sabians (first idolators). He tells us that he has spent much time learning about the Sabian religion (he was sort of an anthropologist). After much study, he discovered that Sabianism revealed cows, so much so, that they prohibited their slaughter:
"As for the slaughter of oxen, the majority of idolaters abominated it, as all of them held this species in very great esteem. Hence you will find that up to our time, the Indians do not slaughter oxen, even in countries where other species of animals are slaughtered." (Guide, 3:46)
Is Maimonides telling us that the Ancient Sabians where Indians, since Hinduism was the first polytheism religion and since Hindus revere/worship cows?
 Though scholars still debate who exactly were the Sabians.