John Wesley on Leviticus 8:36

So Aaron and his sons did all things - And thus the covenant of life and peace, Mal 2:5, was made with them. But after all the ceremonies used in their consecration, one point was reserved for the honour of Christ's priesthood. They were made priests without an oath; but Christ with an oath, Heb 7:21. For neither these priests, nor their priesthood was to continue. But His is a perpetual and unchangeable priesthood.