Jeremias, New Testament Theology, p. 55-56:
"Be that as it may, it is clear that Jesus attached supreme authority to the moment of his baptism. The puzzling and, by that token, early pericope Mark 11.27-33 par. is evidence of that. Jesus is asked about the basis of his authority. His counter-question, whether the baptism of John was or was not from God (v. 30) is hardly an evasion, a move by which Jesus seeks to avoid a direct answer. Now if his counter-question is meant seriously, it means: ' My authority rests on John's baptism', and that again will mean in concrete terms: 'My authority rests on what happened when I was baptized by John'."