According to an opinion of some scholars in Patanjali's time identification of Krishna with Vasudeva is an established fact as is surmised from a passage of the Mahabhasya – ("jaghana kamsam kila vasudevah"). This "supposed earliest phase is thought to have been established from the sixth to the fifth centuries BCE at the time of Pāṇini, who in his Astadhyayi explained the word "vasudevaka" as a bhakta, devotee, of Vasudeva and its believed that Bhagavata religion with the worship od Vasudeva Krishna were at the root of the Vaishnavism in Indian history."