'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.

You shall gird them with sashes, Aaron and his sons, and bind caps on them, and they shall have the priesthood by a perpetual statute. So you shall ordain Aaron and his sons.

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