Some believers automatically associate the book of Deuteronomy with the Law of Moses. If you quote this book as a Christian, they think you're trying to be justified by keeping the law. But, what if you find Jesus in this law?
The Lord will establish you as his holy people, as he promised you on oath, if you keep the commands of the Lord your God and walk in obedience to him. Then all the peoples on earth will see that you are called by the name of the Lord, and they will fear you. - Deuteronomy 28:9-10
...And what if you can find companion verses in the New Testament?
Do not repay evil with evil or insult with insult. On the contrary, repay evil with blessing, because to this you were called so that you may inherit a blessing. For, “Whoever would love life and see good days must keep their tongue from evil and their lips from deceitful speech. They must turn from evil and do good; they must seek peace and pursue it. For the eyes of the Lord are on the righteous and his ears are attentive to their prayer, but the face of the Lord is against those who do evil.” - 1Peter 3:9-12