Moses brought Aaron and his sons, and washed them

The symbolic righteousness of the Mosaic law not only required the High Priest to put on the holy vestments by having his body baptized, but it also commanded his household to be baptised into theirs also. The law reads thus: “This is the thing Jehovah commanded to be done; and Moses brought Aaron and his sons, and washed them with water. And he put upon Aaron the coat, &c.; and he put coats upon his sons, and girded them with girdles, and put turbans upon them, as Jehovah commanded.—(Lev. 8:5, 6, 13; 16:4). Here, as I have said, Moses performed the part of John the Baptizer to Aaron and his sons, who were to be rulers and priests in Israel. Aaron and his family were their nation’s priestly household; and it was the office of the high or chief priest to make atonement or reconciliation, first for himself, then for his household, and lastly for all the congregation of Israel; but admission into the holy and most holy places was only permitted to the baptised; they must bathe their flesh in water, and so put on their holy garments. Hence, all Israel’s priests were immersed persons; and so also all that shall be their priests and kings in the age to come, and have power over the Gentiles, must be immersed likewise.

1917 Christadelphian, 10(electronic ed.), 501–502.