"The later tradition which pretends to have knowledge of all the details of life of Nanak was therefore compelled to put forth as Voucher for its sundry tales and stories, Bhai Bala, who is said to have been the constant companion of Nanak, from his youth days up, whereas our old Janamsakhi does not even once name Bhai Bala. If Bhai Bala had been a constant companion of Nanak and a sort of mentor to him, as he appears now in the current Janamsakhi, it would be quite incomprehensive why never a single allusion should have been made of him in old tradition. “"
January 1, 1970
https://en.wikiquote.org/wiki/Janamsakhis