'Baptize' in the Bible

John answered, saying unto them all, I indeed baptize you with water; but one mightier than I cometh, the latchet of whose shoes I am not worthy to unloose: he shall baptize you with the Holy Ghost and with fire:

and the Pharisee having seen, did wonder that he did not first baptize himself before the dinner.

Was John's authority to baptize from heaven or from humans?"