‘John answered and said, “A man can receive nothing except it has been given him from Heaven. You yourselves bear me witness that I said ‘I am not the Christ (Messiah), but that I am sent before him'.” '
John recognises that each man must do well the task he has been given. He has been given the position of being ‘the voice' preparing the way, and he is satisfied with that. It is Jesus Who has been given the greater task of being the Messiah. John is happy at doing well the job he has been sent to do. There is no room for jealousy under the Kingly Rule of God.
‘A man can do nothing except it has been given him from Heaven.' Nothing, that is, that is worthwhile and effective in God's work. He recognises that Jesus' very success is proof of God working through Him so that John is well content. Indeed he has stressed in his ministry that he is not himself the Messiah but has come to prepare the way for Him (the Christ). Note the constant emphasis on the fact that Jesus is the Christ.