Hebrews 10:30

30 For we know him who said, “It is mine to avenge; I will repay,”a and again, “The Lord will judge his people.”b

Read Hebrews 10:30 Using Other Translations

For we know him that hath said, Vengeance belongeth unto me, I will recompense, saith the Lord. And again, The Lord shall judge his people.
For we know him who said, "Vengeance is mine; I will repay." And again, "The Lord will judge his people."
For we know the one who said, “I will take revenge. I will pay them back.” He also said, “The LORD will judge his own people.”

What does Hebrews 10:30 mean?

John Gill's Exposition of the Bible
Hebrews 10:30

For we know him that hath said
That is, God, whom the apostle and the Hebrews knew; not merely by the works of creation and providence, but by the Scriptures, which they were favoured with, and by which they were distinguished from the Gentiles, and by which they knew his being, nature, and perfections; particularly, that what he said he was able to perform, and that he was true and faithful to every word of his, and to what he has said, ( Deuteronomy 32:35 )

vengeance [belongeth] unto me, I will recompence, saith the Lord.
Vengeance belongs to God, not as to the affection, as if there was any such passion in him; but as to the effect, there being that produced by him, which answers to the effect of such a passion among men, namely punishment: and punishment for sin belongs to God, against whom it is committed; and not to Heathen deities, one of which goes by the name of Vengeance, ( Acts 28:4 ) nor to Satan, and his spiteful angels; nor to men, to exercise it in a private and personal way; though civil magistrates, being in God's stead, are allowed to exercise it in a public way, according to the laws of God: and there is good reason to believe, that what the Lord here says, "I will recompence", or revenge sin, shall be done; which may be concluded from his hatred of sin; from his purity, holiness, and justice; from his faithfulness to his word; from his omnipotence; from the notice he takes of sin, in his own people, in a way of chastisement, and correction; and from the vengeance he has poured on his own Son, as their surety.

And again,
in ( Deuteronomy 32:36 ) the Lord shall judge his people; such as are truly so, his chosen and covenant people, his redeemed and called ones; these he judges by chastising them in a fatherly way, that they may not be condemned with the world; and by governing and protecting them; and by vindicating and pleading their cause, and avenging them on their enemies: or else such as are only his people by profession; on these he will write a "Lo-ammi"; he distinguishes them from his own, and judges between them and his people, and will condemn them; nor will their profession screen them from his wrath and vengeance.

California - Do Not Sell My Personal Information  California - CCPA Notice