Mark 2:24

And the Pharisees said unto him
To Christ, the same they said to his disciples, ( Luke 6:2 ) .

Behold, why do they on the sabbath day, that which is not lawful?
see how they pluck the ears of corn and rub them, and eat things, which by the law, especially by the traditions of the elders, were not lawful to be done on the sabbath day; (See Gill on Matthew 12:2).