‘For we know him who said, “Vengeance belongs to me, I will recompense.” And again, “The Lord shall judge his people.” It is a fearful thing to fall into the hands of the living God.'
And, he says, we can see this clearly for ourselves, for we know Him as He is and as He is revealed to be by the Scriptures which say, ‘Vengeance belongs to Me, I will repay' (a translation and adaptation of Deuteronomy 32:35; compare Romans 12:9 which suggests it had taken on a standard form). The Hebrew says, ‘Vengeance is Mine, and recompense' which indicates the same thought. Note both the fact and the warning. Vengeance is His, that is the fact. He will repay, that is the warning.
His second quotation is ‘The Lord will judge His people' (Deuteronomy 32:36). This includes both beneficent ‘judging' as with the ‘judges', and condemning judgments as Judge of all the world. It is an assurance to those who are faithful to Him, that He will rule them and watch over them as they come under the Kingly Rule of God, and brings cold fear on those who sin with a high hand as the Day of Judgment draws near. Thus we know that He will certainly, in accordance with His own will, judge those who have called themselves His people and bring vengeance on those who rebel. It is telling them that the very words that declare their judgment are taken from the very Law to which they claim to be returning.
And he adds the solemn reminder, ‘It is a fearful thing to fall into the hands of the living God.' For ‘it is a fearful thing' compare the ‘fearful looking for of judgment' in Hebrews 10:28. God is not mocked, not to be treated lightly. For those who have returned to dead works and to a now invalid and dead ritual, to fall into the hands of ‘the living God' can only be a fearful thing, for God will require it at their hands, especially in view of what they have rejected.
These words are not cited as a quotation. However, some of the wording, although not the direct idea, is taken from 2 Samuel 24:14; 1 Chronicles 21:13 in LXX, where the thought is that David prefers to fall into the hands of ‘the Lord' because He at least is both just and compassionate. He trusts God and fears men. It is a very different for those who have permanently turned away from Him by rejecting His Son to shame and humiliation. For them facing up to Him is the most fearful thing that is possible
‘To fall into the hands of ‘the living God'.' The fact of the ‘living' God is emphasised to bring about the realisation that, because He is unlike the dead gods of other religions, they can be sure that the living God will undoubtedly exercise justice against them (compare the warning in Hebrews 3:12). They have previously declared themselves as servants of the living God (Hebrews 9:14). Now they are runaways from One Who is aware of all they do. He will not look lightly on their rejection of His Son.