'Perpetual' in the Bible

These must be on Aaron and his sons when they enter to the tent of meeting, or when they approach the altar to minister in the Holy Place, so that they bear no iniquity and die. It is to be a perpetual ordinance for him and for his descendants after him.

and wrap the sashes around Aaron and his sons and put headbands on them, and so the ministry of priesthood will belong to them by a perpetual ordinance. Thus you are to consecrate Aaron and his sons.

It is to belong to Aaron and to his sons from the Israelites, by a perpetual ordinance, for it is a contribution. It is to be a contribution from the Israelites from their peace offerings, their contribution to the Lord.

they must wash their hands and their feet so that they do not die. And this will be a perpetual ordinance for them and for their descendants throughout their generations."

The Israelites must keep the Sabbath by observing the Sabbath throughout their generations as a perpetual covenant.