Albert Barnes Commentary 1 Corinthians 15:25

"For he must reign, till he hath put all his enemies under his feet." — 1 Corinthians 15:25 (ASV)

For he must reign. It is fitting, or proper, (dei) that he should reign until this is accomplished. It is proper that the mediator kingdom should continue until this great work is brought about. The word "must" here refers to the propriety of this continuance of his reign, and to the fact that this was contemplated and predicted as the work which he would accomplish. He came to subdue all his enemies. See Psalm 2:6-10; Psalms 110:1, The Lord said unto my Lord, Sit thou at my right hand until I make thine enemies thy footstool. Paul, doubtless, had this passage in mind as affirming the necessity that he should reign until all his enemies should be subdued. That this refers to the Messiah is abundantly clear from Matthew 22:44-45.