'Perpetual Statute' in the Bible

The sons of Aaron, the priests, shall blow the trumpets; and the trumpets shall be for you a perpetual statute throughout your generations.

The one who gathers the ashes of the heifer shall wash his clothes, and be unclean until evening. This shall be a perpetual statute to the Israelites and to the stranger who lives as a resident alien among them.

So it shall be a perpetual statute to them. He who sprinkles the water for impurity [on another] shall wash his clothes, and he who touches the water for impurity shall be unclean until evening.