The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance. The Lord is not slack - They probably in their mocking said, "Either God had made no such promise to judge the world, destroy the earth, and send ungodly men to perdition; or if he had, he had forgotten to fulfill it, or had not convenient time or leisure." To some such mocking the apostle seems to refer: and he immediately shows the reason why deserved punishment is not inflicted on a guilty world.
But is long-suffering - It is not slackness, remissness, nor want of due displacence at sin, that induced God to prolong the respite of ungodly men; but his long-suffering, his unwillingness that any should perish: and therefore he spared them, that they might have additional offers of grace, and be led to repentance - to deplore their sins, implore God's mercy, and find redemption through the blood of the Lamb.
As God is not willing that any should perish, and as he is willing that all should come to repentance, consequently he has never devised nor decreed the damnation of any man, nor has he rendered it impossible for any soul to be saved, either by necessitating him to do evil, that he might die for it, or refusing him the means of recovery, without which he could not be saved.