Adam Clarke on John 3:27

A man can receive nothing, etc. - Or, A man can receive nothing from heaven, unless it be given him. I have received, not only my commission, but the power also by which I have executed it, from above. As I took it up at God's command, so I am ready to lay it down when he pleases. I have told you from the beginning that I was only the forerunner of the Messiah, and was sent, not to form a separate party, but to point out to men that Lamb of God which takes away the sin of the world: Joh 3:28.