30 For we know Him who said, “Vengeance is Mine, I will repay,” says the Lord. And again, “The Lord will judge His people.” 31 It is a fearful thing to fall into the hands of the living God.
Verses 26-29 concludes with an appeal to the Word of God by quoting Deuteronomy 32 in verse 30 and 2 Samuel 24:14 in verse 31.
The point of the word “for” is to show that the warning of the previous verses was no idle threat.
we know Him who said,
The following is a quotation from Deuteronomy 32:35-36 where God said that He will severely judge those who reject His Covenant. This chapter of Deuteronomy portrays God’s retributive judgments on His people (Deut 32:19-27). A true understanding of God shows that He does not sanction distortion of truth.
“Vengeance is Mine,
God reserves the right to execute judgment on “His people.”
I [emphatic] will repay,” says the Lord.
God will “repay” believers who violate the New Covenant with temporal discipline (Deut 32:35). God will assume the responsibility for vengeance.
The second quotation is from the Septuagint Deuteronomy 32:36.
“The Lord will judge His people.”
God will vindicate His people by judgment against His enemies. He will do this by impartial critique of the facts.
“His people” are God’s people, true believers.
It is a fearful thing
The “fearful thing” is God’s judgment (He 10:27). God is absolute and unequivocal in His assessment of the facts because He is omniscient.
to fall into the hands of the living God.
“To fall” into the living God’s hands is to come under His absolute authority. David would rather be judged by God than man (2 Sam 24:14). In David’s case God sent pestilence that caused 70 thousand Israelites to die. Falling into the hands of God here is chastisement, not eternal damnation. This is a warning to believers, not unbelievers.
God takes upon Himself the responsibility for dealing with believers who distort doctrine.
God offers no idle threats. He will judge His people in grace otherwise His justice would be overwhelming to the individual. There is a difference between chastisement and punishment.