Appearing on the scene almost out of nowhere to bless Abraham and then disappearing almost as soon as he arrived, Melchizedek is one of the more enigmatic figures recorded in Scripture (Gen. 14:17–20). Because he blessed Abraham, the greatest of all the patriarchs, the God-inspired authors who penned the Scriptures understood that Melchizedek must have had a special role in the covenant community. This role is unfolded in great detail throughout the book of Hebrews, but the author of that epistle was not the first person to consider the importance of that priest-king who blessed Abraham. Centuries before the author of Hebrews wrote, David referred to Melchizedek in Psalm 110.
Psalm 110:4 indicates that the greatness of Melchizedek is not limited to the man himself but belongs to an entire order of priests who follow after him. So great is his role that Melchizedek’s priestly order is an eternal one, or perhaps more accurately, there is one member of this order who will hold the priesthood forever. But this individual is not merely a priest; he is also a descendant of David and so is a king as well.
That there would be a king who would also hold the priestly office is actually foreshadowed in David himself, who on occasion performed priestly roles such as wearing an ephod and offering sacrifices (2 Sam. 6:14–19). But these were isolated instances, and in general the roles of priest and king were distinguished in the Old Testament. Nevertheless, that they could be combined in David, at least for a time, led to a hope that they finally would be combined permanently in David’s greatest descendant, namely, the Messiah. Consequently, the King of kings and Lord of lords is also the Great High Priest who has atoned for the sins of all His people. We obey the Lord Jesus as our king, but we also enter into His kingdom through His sacrifice (Heb. 9:1–10:18).
Psalm 110 concludes with an emphasis on the power and might of the Davidic king, the Messiah who protects His people. Thus, we see a difference between how the Messiah treats His own and how He treats those outside His kingdom. John Calvin comments, “As a shepherd is gentle towards his flock, but fierce and formidable towards wolves and thieves; in like manner, Christ is kind and gentle towards those who commit themselves to his care, while they who willfully and obstinately reject his yoke, shall feel with what awful and terrible power he is armed.”