In the consideration of this remarkable scripture, it should be noted that the word "afflictions" ("afflictions of Christ") is never found elsewhere in connection with our blessed Lord. But it is constantly used of the saints, and indicates the trials, persecutions, tribulations, etc., that come upon them from without in consequence of their confession of Christ, and of fidelity to Him in the midst of an evil world. The point is important, as conclusively showing that these afflictions of Christ are altogether apart from His sufferings on the cross, when making atonement. They are rather the sufferings He endured in His whole pathway of doing the will of God, but viewed here as encountered through His love to the Church. He "loved the church, and gave Himself for it," and this entailed upon Him these afflictions which came upon Him through the instrumentality of man in the hands of Satan.
The Apostle Paul through grace was animated by the same love, however inferior the degree; and he could thus write, "I endure all things for the elect's sake, that they may also obtain the salvation which is in Christ Jesus with eternal glory." 2 Tim. 2:10. He labored and suffered for the same object as his blessed Master. This gives at once the key to our scripture. Here he says, I "rejoice in my sufferings for you," that is, for you Gentiles—sufferings which came upon him peculiarly in connection with his ministry of the truth of the one body, exciting as it did the deadly enmity of the Jews. Inasmuch, therefore, as the Word of God was not completed until the truth of the Church was promulgated, Paul as its minister suffered in an especial manner for Christ's "body's sake, which is the church," and could thus say, since he participated in them, that he filled up that which was behind of the afflictions of Christ. They were Christ's own afflictions; and Paul filled up, so to speak, their measure. In principle, if a servant now suffers in the same way, from the same motive, and for the same object, he would be sharing in, if not filling up, that which is behind of these afflictions of Christ.