Aaron, three years older than Moses, was set apart by God as Moses's spokesman before Pharaoh. When Israel reached Sinai he was consecrated as the first high priest, and his sons after him — the line that served at the altar of the Tabernacle and the Temple until AD 70.
He failed gravely once, fashioning the golden calf while Moses was on the mountain. Yet God spared him at the intercession of Moses. The Lord vindicated his priesthood when his rod budded, blossomed, and bore almonds in the Tabernacle overnight (Num 17).
On Mount Hor in Edom, Moses stripped him of his priestly vestments and placed them on his son Eleazar; Aaron died on the summit at one hundred and twenty-three. Israel mourned him thirty days.
The Letter to the Hebrews presents Christ as the great High Priest after the order of Melchizedek, surpassing Aaron's priesthood yet fulfilling it.