Know therefore that the LORD your God is God, the faithful God who keeps covenant and steadfast love with those who love him and keep his commandments, to a thousand generations —Deuteronomy 7:9
In chapter 11 of Future Grace John Piper clarifies a major difference between the old covenant and the new—
The fact that we live in this new day under the new covenant should fill us with joy. But our joy should not be at the expense of Old Testament truth. Sometimes, to exalt our precious privilege as beneficiaries of the new covenant, we will over-criticize the old covenant. But what we are seeing in this chapter is that the old is not deficient because it was a commanding covenant, or because it commanded wrong things. It was deficient because it was not accompanied, by and large, with inner, transforming, enabling divine power (see Romans 8:3) (p. 148).
It is a mistake to think that all the commands of the Bible are only found in the Old Testament. The fundamental difference in the New Covenant is that it’s characterized by the Holy Spirit who empowers believers to believe and obey God.
There was a remnant throughout the history of Israel who understood the need to look away from themselves for this spiritual enabling. Piper writes of them:
They knew that without the empowering future grace of God, given in answer to prayer, they would not be able to see the wonders of God in his Word [Psalm 119:18]. And they knew that without the sovereign heart-inclining grace of God, they would drift away from him into the love of money [Psalm 119:36]. They prayed for the future grace of joy and a clean heart and a steadfast spirit; and that God himself would make them willing to do what he commands (p. 146).