Luke 20:3 Meaning

1And it came to pass, that on one of those days, as he taught the people in the temple, and preached the gospel, the chief priests and the scribes came upon him with the elders,

2And spake unto him, saying, Tell us, by what authority doest thou these things? or who is he that gave thee this authority?

3And he answered and said unto them, I will also ask you one thing; and answer me:

4The baptism of John, was it from heaven, or of men?

5And they reasoned with themselves, saying, If we shall say, From heaven; he will say, Why then believed ye him not?