8 And who is it, says some one, that is thus slain by the sweet savor? It is to this the apostle alludes in the words, “And who is sufficient for these things?” In what wonderful ways God brings it about that the good savor is fraught both with life to the good, and with death to the wicked; how it is so, so far as the Lord is pleased to inspire my thoughts (for it may still conceal a deeper meaning beyond my power to penetrate)—yet so far, I say, as my power of penetration has reached, you ought not to have the information withheld.
The integrity of the Apostle Paul's life and conduct, his preaching of righteousness in word and exhibition of it in works, his wondrous power as a teacher and his fidelity as a steward, were everywhere noised abroad: he was loved by some, and envied by others. For he himself tells us in a certain place of some, that they preached Christ not sincerely, but of envy; “thinking,” he says, “to add affliction to my bonds.” But what does he add? “Whether in pretence or in truth, let Christ be preached.” They preach who love me, they preach who hate me; in that good savor the former live, in it the others die: and yet by the preaching of both let the name of Christ be proclaimed, with this excellent savor let the world be filled.
Have you been loving one whose conduct evidenced his goodness then in this good savor you have lived. Have you been envying such a one? Then in this same savor you have died. But have you, pray, in thus choosing to die, converted this savor into an evil one? Turn from your envious feelings, and the good savor will cease to slay you.
Source: Tractates on the Gospel of John (New Advent)