Exodus 12:14

12:14 This day will become a memorial for you, and you will celebrate it as a festival to the Lord – you will celebrate it perpetually as a lasting ordinance.

Exodus 29:9

29:9 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.

Exodus 40:15

40:15 and anoint them just as you anointed their father, so that they may minister as my priests; their anointing will make them a priesthood that will continue throughout their generations.”