And he said unto them
 By way of answer to their question, and which was a full one, and enough to silence them: 
 have ye never read what David did;
 referring to the history in ( 1 Samuel 21:1-15 ) . 
 when he had need:
 of bread, was in great necessity, and in the utmost distress: 
 and was an hungered, he, and they that were with him?
 which was a justifiable reason for what he and his company did; as it was for the action of the disciples; being in a like case, and therefore very appropriate to the purpose; (See Gill on Matthew 12:3).