Matthew 21:28 Meaning

26But if we shall say, Of men; we fear the people; for all hold John as a prophet.

27And they answered Jesus, and said, We cannot tell. And he said unto them, Neither tell I you by what authority I do these things.

28But what think ye? A certain man had two sons; and he came to the first, and said, Son, go work to day in my vineyard.

29He answered and said, I will not: but afterward he repented, and went.

30And he came to the second, and said likewise. And he answered and said, I go, sir: and went not.