Mat 12:7 But if you knew what [this] means: I will have mercy, and not sacrifice, you would not condemn the guiltless.

This is an historically pivotal verse in Christ's teachings, but you very seldom hear anyone comment on it, even among those who focus on Christ's words. This statement marks the transition from Old Testament worship, in the form of offering sacrifices at the temple, to New Testament worship in the form of treating your fellow humans more mercifully. And he does this, not by contradicting out the Old Testament but by quoting it.

"Knew" is gignôskô (ginosko) which means "to learn to know," "to know by reflection or observation," and "to perceive."

"Mercy" is eleos, which means "pity," "mercy," and "compassion."

"Sacrifice" is thusia. which means "a burnt-offering," "a sacrifice," and "a victim of sacrifice." While in English, we have the idea of "personal sacrifice" to mean voluntarily giving up something for the benefit of another, this was not the sense of this word. This word focuses on the destruction of something of value to satisfy the gods. The word, hiereuô, means "to slaughter," and it is the basis of the words used by Matthew for priest, hiereus and temple, hieron, though both of these later words came to mean "holy" and "wonderful" by the time of Christ.

In this first part of this verse, Christ is quoting from the Old Testament:
Hsa 6:6 For I desired mercy, and not sacrifice; and the knowledge of God more than burnt offerings.

In the Hebrew, "desire" is chaphets, which means "to delight in," "to take pleasure in," and "to be pleased with."

In the original Hebrew, "mercy" is checed, which means "goodness," "kindness," and "faithfulness." It also means "to be ashamed" and "a reproach." Based on the verb checed ("to be kind"), the adjective combines both the idea of being good and feel guilty if you are not good.

In Hebrew, "sacrifice" is zebach, ("a sacrifice") which is the noun form of zabach, which means "to slaughter" either for sacrifice or for eating.

But the original gets more specific, pairing "mercy" with "knowledge of God" which in Hebrew is da`ath ("knowledge," "perception," and "wisdom") 'elohiym (gods, divine ones, God). It also pairs "sacrifice" with olah, that is, "a burnt offering."

In the second part of this verse, Christ goes on to say that because people don't understand what God wants, they condemn the guiltless.

"Condemn" is katadikazô, which means "to give judgment against," "to pass a sentence," and "to condemn."

"Guiltless" is anaitios, which means "not being at fault," "guiltless," and "not being the cause" of something. It means literally "not the cause." We saw this word used just a few verses ago to describe the priests who violate the Sabbath by working.

Here, Christ in this short phrase announces the new era where religion, for the first time in human history will be defined by compassion. While people today in almost every religion accept the basic idea that religion means having compassion for your fellow humans, hardly anyone realizes that this idea was completely novel when Christ introduced it. Until Christ, religions were about getting power from the gods or at least being protected from them.

However, this line is not only historically significant, it is also extremely clever because in this short phrase Christ both announces compassion as the new standard for worship AND condemns those attacking him for their lack of compassion. The ease with which Christ's words work on several different levels is one of the reasons studying his words makes me a stronger believer.