Charles Ellicott Commentary Matthew 12:5

"Or have ye not read in the law, that on the sabbath day the priests in the temple profane the sabbath, and are guiltless?" — Matthew 12:5 (ASV)

The priests in the temple profane the sabbath—The work of the priests, as described for example in Numbers 28:9, involved sacrificing animals and placing the shewbread. This involved an amount of labor that, in any other kind of work, would have broken the Sabbath rest; yet no one blamed the priests, because they were serving in the Temple of Jehovah.