Mark 2:25

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).