Mark 11:29-33

29And Jesus answering said to them, I also will ask you one thing, and answer me, and I will tell you by what authority I do these things: 30The baptism of John, was it of heaven, or of men? answer me. 31And they reasoned with themselves, saying, If we should say, Of heaven, he will say, Why [then] have ye not believed him? 32but should we say, Of men — they feared the people; for all held of John that he was truly a prophet. 33And they answering say to Jesus, We do not know. And Jesus [answering] says to them, Neither do I tell you by what authority I do these things.