Numbers 19:1
The LORD spoke to Moses and Aaron, saying, 'This is the statute of the law that the LORD has commanded' — the red heifer ordinance opens with solemn divine authority, introducing the most mysterious of all Mosaic laws. The chok (statute) stands without rational explanation, a divine mystery embedded in Israel's purification system. This law governs the entire wilderness period and beyond: how the ritually unclean become clean again, how death's contamination is reversed.