Matthew 12:1-3

At that time Jesus went on the sabbath day through the corn; and his disciples were an hungred, and began to pluck the ears of corn, and to eat. 

But when the Pharisees saw it, they said unto him, Behold, thy disciples do that which is not lawful to do upon the sabbath day. 

But he said unto them, Have ye not read what David did, when he was an hungred, and they that were with him;