And they answered and said unto Jesus
 Being reduced by this dilemma to the greatest streight and difficulty; 
 we cannot tell:
 they could, if they would, but they did not care to tell; they knew if they did, they should expose themselves one way or other: 
 and Jesus answering, saith unto them, neither do I tell you by what
 authority I do these things; (See Gill on Matthew 21:27).