John Gill Commentary Luke 6:2

"But certain of the Pharisees said, Why do ye that which it is not lawful to do on the sabbath day?" — Luke 6:2 (ASV)

And certain of the Pharisees said to them
To the disciples. The Evangelists Matthew and Mark say, that they said this to Jesus: no doubt but they said it to both, first to one, and then to the other; probably last of all to Christ, who returned an answer to it:

why do you that which is not lawful on the sabbath day?
as to pluck ears of corn, and rub them, and eat them; (See Gill on Matthew 12:2)