John Calvin Commentary Genesis 15:14

"and also that nation, whom they shall serve, will I judge: and afterward shall they come out with great substance." — Genesis 15:14 (ASV)

Also that nations whom they serve. A consolation is now added, and the first point is this: God testifies that He will be the vindicator of His people. From this it follows that He will take upon Himself the care for the salvation of those whom He has embraced, and will not allow them to be harassed by the ungodly and the wicked without punishment.

And although He here clearly announces that He will take vengeance on the Egyptians, yet all the enemies of the Church are exposed to the same judgment. Indeed, Moses in his song extends to all ages and nations the threat that the Lord will exact punishment for unjust persecutions.

Vengeance is mine, I, He says, will repay,
(Deuteronomy 32:35).

Therefore, whenever we are treated inhumanly by tyrants (which is very common for the Church), let this be our consolation, that after our faith has been sufficiently proven by bearing the cross, God, by whose will we are thus humbled, will Himself be the Judge, who will repay our enemies the due reward for the cruelty they now exercise.

Although they now exult with intoxicated joy, it will eventually become clear from the outcome itself that our miseries are happy ones, but their triumphs wretched; because God, who cares for us, is their adversary. But let us remember that we must leave room for the wrath of God, as Paul exhorts, so that we are not driven headlong to seek revenge.

Room must also be made for hope, so that it may sustain us when we are oppressed and groaning under the burden of evils. To judge the nation means the same thing as to summon it to judgment, so that God, after He has long remained silent, may openly manifest Himself as the Judge.