exodus 28:1 And take thou unto thee Aaron thy brother, and his sons with him, from among the children of Israel, that he may minister unto me in the priest's office, even Aaron, Nadab and Abihu, Eleazar and Ithamar, Aaron's sons. - Free Bible Online

      Ex 28:1-43. APPOINTMENT TO THE PRIESTHOOD.

      1. take thou unto thee Aaron thy brother, and his sons with him--Moses had hitherto discharged the priestly functions (Ps 99:6), and he evinced the piety as well as humility of his character, in readily complying with the command to invest his brother with the sacred office, though it involved the perpetual exclusion of his own family. The appointment was a special act of God's sovereignty, so that there could be no ground for popular umbrage by the selection of Aaron's family, with whom the office was inalienably established and continued in unbroken succession till the introduction of the Christian era.

JFB.