'Baptize' in the Bible

I indeed baptize you with water unto repentance: but he that cometh after me is mightier than I, whose shoes I am not worthy to bear: he shall baptize you with the Holy Ghost, and with fire:

Where did John's authority to baptize come from? From heaven or from humans?"

Go therefore and make disciples of all the nations; baptize them into the name of the Father, and of the Son, and of the Holy Spirit;