Deuteronomy 7:10

and who repayeth to them who hate Him the reward of their good works in this world, to destroy them (for their evil works) in the world to come; neither delayeth He (to reward) His enemies, but while they are alive in this world He payeth them their recompense.

He repays His enemies [plural] every one of his enemies (as in, “the righteous [plural] are secure [singular] like a lion” [Proverbs 28: 1] [cf. comment on Leviticus 19: 8])

to his face i.e., to himself, personally. Some people also compare the word to “in His face”, a Hebrew metaphor for “in His anger” [cf. comment on Leviticus 26: 17], meaning that He will punish His enemies for having made themselves enemies of the Truth.

to destroy him; for his enemy He does not defer Some interpret the verse to mean that the wicked are rewarded in this world for the good they have done, and He does not defer their reward for the World to Come. In my opinion, though, the correct interpretation contrasts the wicked against the righteous. Unlike them, who endure “a thousand generations” [: 9], God ’s enemies will perish, and will not continue into the future, although they may falsely expect their children or their grandchildren to survive (see “to the third and fourth generation” [Exodus 20: 5]).

ומשלם לשונאיו. retribution for its sins.

אל פניו, during their lifetime, not that of their children or children’s children. לא יאחר, either in his lifetime, or latest to the fourth generation. This is the plain meaning of the text. This is virtuous act, as Rashi says, that by letting the sinner die for sins (prematurely) it preserves his afterlife if the guilty party had repented his errors. G’d does not enact retribution for sins committed more that four generations ago. On the other hand, reward is paid even many generations later than merely four generations after the good deed had been performed. Even if the intervening generations had been sinful, this does not cancel out a reward G’d had not paid for the good deeds of the ancestor. If, eventually, a righteous person emerges from a sinful family, such a righteous person will become the beneficiary of merits accumulate by his ancestor who G’d had not yet repaid for this.

ומשלם לשונאיו אל פניו, “but He will make a reckoning with those who hate Him to their face,” i.e. He will make a reckoning immediately and not wait one thousand generations for their descendants to become penitents. But as soon as such people become penitents, they will become the beneficiaries of My promises to their forefathers. Therefore, as Moses said in Deuteronomy 7,12: והיה עקב תשמעון וגו', “it will come to pass as an immediate result of your listening to My voice that all My promises will be showered upon you.”