Should men quarrel and a man strike his fellow man… he shall pay for his loss of time, and he shall pay for his cure. The additional context “should men quarrel” is immaterial to the law. It was mentioned to teach us, says the Midrash, that “no good or peace” comes from a quarrel and adds that the world’s first murder began as a lofty quarrel. Cain and Abel were arguing, claims the Midrash, over where the Temple would be built. The end was that Abel lost his life and Cain was sent to wander the earth.