Neither Mark nor Luke have this argument of our Saviour’s. The meaning is, all acts of servile labour are not unlawful on the sabbath day. The priests, according to the law, Num_28:9, offer sacrifices, and do many other acts, such as circumcising, and many other things, which in your sense would be a profanation of the sabbath; yet you do not blame them, neither are they to he blamed, because God permitted and directed them.
If any say, "But how doth this agree to what our Saviour is speaking to?"
Answer: The disciples of Christ were employed with and by him in going about and preaching the gospel, and what they now did was but in order to fit them for his work, when they had not had such leisure as others beforehand to provide: and this establisheth a second rule, That works of piety, and tending to fit us for acts of piety, that cannot conveniently be done before, are lawful on the sabbath day.