For if God did not spare angels when they sinned, but cast them into hell and committed them to chains of gloomy darkness to be kept until the judgment;
4. For if. We have stated how much it behoves us to know that the ungodly, who by their mischievous opinions corrupt the Church, cannot escape God’s vengeance; and this he proves especially by three remarkable examples of God's judgment, — that he spared not even angels, that he once destroyed the whole world by a deluge, that he reduced Sodom to ashes, and other neighboring cities.
Men are apt to think that a reprieve is the forerunner of a pardon, and that if judgment be not speedily executed it is, or will be, certainly reversed. But the apostle tells us that how successful and prosperous soever false teachers may be, and that for a time, yet their judgment lingereth not. God has determined long ago how he will deal with them.
Commenting on 2 Peter 2:3-6
For if God spared not the angels that sinned..... By whom are meant the devil and his angels; who are spirits created by God and as such were good; their first estate which they left was pure and holy, as well as high and honourable; they, were at first in the truth, though they abode not in it; they were once among the morning stars...