Ps 110:4

110:4 the order of Melchizedek. The regular priesthood of Israel was from Aaron, and their duties were limited to religious worship. Little is known about Melchizedek (Gen. 14:18–20), but it appears that he combined the functions of king and priest. David also combined these functions to an extent. Jesus Christ is both King and Priest, though not descended from the line of Aaron (Heb. 5:6; 7:17; 8:1; 10:12–14).