'Perpetual Statute' in the Bible

In the tent of meeting, outside the veil which is before the testimony, Aaron and his sons shall keep it in order from evening to morning before the Lord; it shall be a perpetual statute throughout their generations for the sons of Israel.

And thou shalt gird them with girdles, Aaron and his sons, and put the bonnets on them: and the priest's office shall be theirs for a perpetual statute: and thou shalt consecrate Aaron and his sons.

They shall wash their hands and their feet, so that they will not die; it shall be a perpetual statute for them, for Aaron and his descendants throughout their generations.”