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?

This reference is to the fact than an exception was made for the priests who served in the temple, and who could, therefore, do work on the sabbath that would otherwise have been unlawful. Christ's stress on that exception called attention to an analogy between himself and the temple. He referred to his body as "the temple," stating that he would raise it up in three days (John 2:19). The argument is that, just as the priests served the temple on the sabbath day and were guiltless, his disciples might also serve Christ, the Greater Temple, without incurring guilt. Thus, even if his disciples had violated the sabbath restrictions (which they had not done), their doing so in the service of Christ would have granted them exemption. "Profaning" the sabbath does not refer to any actual profanation, but means that their actions, if performed otherwise than in temple service, would have profaned it.