Contradiction with Romans 3:20
While Deuteronomy 30:8 speaks of obeying the commandments for life and prosperity, Romans 3:20 suggests that no one can be justified by the law itself, as it brings the knowledge of sin.
Romans 3:20: Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law [is] the knowledge of sin.
Contradiction with Galatians 2:16
Deuteronomy 30:8 emphasizes returning to God and obeying His voice, but Galatians 2:16 states that a person is justified by faith in Jesus Christ and not by the works of the law.
Galatians 2:16: Knowing that a man is not justified by the works of the law, but by the faith of Jesus Christ, even we have believed in Jesus Christ, that we might be justified by the faith of Christ, and not by the works of the law: for by the works of the law shall no flesh be justified.
Contradiction with Romans 10:4
Deuteronomy 30:8 implies a return to the law's observance, whereas Romans 10:4 declares Christ as the end of the law for righteousness to everyone who believes.
Romans 10:4: For Christ [is] the end of the law for righteousness to every one that believeth.
Contradiction with Hebrews 8:13
This verse indicates the obsoleteness of the old covenant (and its laws), contrasting with Deuteronomy 30:8's emphasis on adherence to the law.
Hebrews 8:13: In that he saith, A new [covenant], he hath made the first old. Now that which decayeth and waxeth old [is] ready to vanish away.
Contradiction with Galatians 3:10
Where Deuteronomy 30:8 underscores the need to follow the commandments, Galatians 3:10 warns that those who rely on the law are under a curse, as it is impossible to uphold it perfectly.
Galatians 3:10: For as many as are of the works of the law are under the curse: for it is written, Cursed [is] every one that continueth not in all things which are written in the book of the law to do them.