Luke 20:4 The baptism of John, was it from heaven, or of men?
The chief priests, scribes and elders were looking for a gotcha on Jesus. In fact, they'd really been after Him since He raised Lazarus from the dead. Now He really got their goat by cleansing the temple of the vermin making merchandise off the visiting worshipers. If you want to get under somebody's skin, mess with their wallets.
But Jesus turned the tables (pun intended) on them by asking this question about John's baptism. Either answer they gave would put them in a pickle, so they just folded their arms and pouted.
They should never have come to a battle of wits with God in the flesh, especially when they were so unequipped. It is like bringing a knife to a gun fight. I am reminded of Job 9:3 "If he will contend with him, he cannot answer him one of a thousand."
Lesson to be learned, don't argue with God, you will never win.