Charles Ellicott Commentary Matthew 12:7

"But if ye had known what this meaneth, I desire mercy, and not sacrifice, ye would not have condemned the guiltless." — Matthew 12:7 (ASV)

I will have mercy, and not sacrifice — A third argument follows from the Old Testament (Hosea 6:6). The teachers or interpreters of the Law had failed to grasp the meaning of the prophets' simplest statements. Mercy and not sacrifice—moral duties, not ceremonial ones—these constitute the true life of religion and are what is truly acceptable to God. It was because they had inverted the proper relationship between these two that they condemned, in this instance, those whom our Lord declares to be absolutely guiltless.