John Chrysostom

"But the other of love, knowing that I am set for the defense of the Gospel." What means, "that I am set for the defense of the Gospel"? It is, They are preparing for the account which I must give to God, and assisting me. What is meant by "for the defense"? I have been appointed to preach, I must give account, and answer for the work to which I have been appointed; they assist me, that my defense may be easy; for if there be found many who have been instructed and have believed, my defense will be easy. …

Homily on Philippians 2 ↗

Theophylact of Ohrid

That is, others out of love both for God and for me preach the Gospel, knowing that I must give an account of my preaching, and for this reason they assist me in this work. For if many join my preaching, it will be easy for me to defend the Gospel. In this way they assist me, teaching many.

Commentary on Philippians ↗

Thomas Aquinas

Then the Apostle explains what he had said, saying that, the former proclaim Christ out of partisanship and not according to a right intention. For their depraved intention is clear in two ways: first, by preaching publicly they caused a disturbance among the Gentiles against the Apostle and thus added to the affliction he already had; secondly, because they believed that Paul would be disturbed, when he heard that they were usurping the task committed to him, thereby adding more affliction to one already afflicted.

Commentary on Philippians ↗