Albert Barnes Commentary Colossians 1:24

"Now I rejoice in my sufferings for your sake, and fill up on my part that which is lacking of the afflictions of Christ in my flesh for his body`s sake, which is the church;" — Colossians 1:24 (ASV)

Who now rejoice in my sufferings for you. This means for you as a part of the Gentile world. It was not for the Colossians alone; he regarded himself as suffering on account of his labors in preaching to the Gentiles at large. His trials at Rome had come upon him because he had maintained that the wall of partition between Jews and Gentiles was broken down, and that the gospel was to be preached indiscriminately to all humanity. (See this illustrated in the Introduction, section 5.)

And fill up that which is behind of the afflictions of Christ. This means what I lack to equal the sufferings Christ endured in the cause of the church. The apostle seems to mean:

1. That he suffered in the same cause for which Christ suffered.
2. That he endured the same kind of sufferings—to some extent—in reproaches, persecutions, and opposition from the world.
3. That he had not yet suffered as much as Christ did in this cause; and, though he had suffered greatly, there was still much lacking to make him equal to the Savior in this respect; and,
4. That he felt it was an object to be earnestly desired to be made in all respects just like Christ, and that in his present circumstances he was rapidly filling up what was lacking, so that he would have a more complete resemblance to Him. What he says here is based on the leading desire of his soul—the great principle of his life—TO BE JUST LIKE CHRIST: alike in moral character, in suffering, and in destiny. (See Barnes on Philippians 3:10).

Having this strong wish, he had been led to pursue a course of life that conducted him through trials strongly resembling those Christ Himself endured. As rapidly as possible, he was filling up that in which he now fell short. He does not mean that there was anything lacking or deficient in the sufferings Christ endured in making an atonement, which was to be supplied by His followers, so that their merits might be added to His to secure the salvation of men, as the Romanists seem to suppose. Rather, he means that there was still much lacking on his part before he would be entirely conformed to the Savior in His sufferings, and that his present condition was such as to rapidly fill that up.

This seems to me to be the fair meaning of this expression, though not the one commonly given. The usual interpretation is, "that which remains to me of affliction to be endured in the cause of Christ." But this interpretation seems cold and tame to me, and not to suit the genius of Paul.

In my flesh. This refers to bodily sufferings.

For his body's sake, which is the Church. (See Barnes on Ephesians 1:23).