Then it will come about, when many evils and troubles find them, that this song will testify before them as a witness (for it shall not be forgotten from the mouth of their descendants); for I know their inclination which they are developing today, before I bring them into the land which I swore. (v. 21)

For I know that after my death you will behave very corruptly and turn from the way which I have commanded you; and evil will confront you in the latter days, because you will do that which is evil in the sight of the Lord, provoking Him to anger with the work of your hands. (v. 29)

God did not give the law to the Israelite for them to be saved by keeping the law. The law was given to them to know God’s plan of salvation through Jesus Christ. But only few understood it. For those who are not given the Holy Spirit, knowing God and His plan is impossible. Thus, they rely on the law but are lawbreakers. The law is a curse because God did not give the law as a way to salvation. God did not give all people the new heart.

Take this Book of the Law and place it beside the ark of the covenant of the Lord your God, so that it may remain there as a witness against you. (v. 26)

The law was not given as a witness for the Israelites. It was a witness against them. No one received salvation through the law. The old covenant must fail so that the new covenant can be introduced. However, the new covenant is older because God planned this before the foundation of the world. The new covenant is the one and only eternal covenant between God and His people. Being biological descendants of Abraham does not mean that they are God’s people. Concerning this, the Book of Galatians explains in detail.

And you, brothers and sisters, like Isaac, are children of promise. But as at that time the son who was born according to the flesh persecuted the one who was born according to the Spirit, so it is even now. But what does the Scripture say? “DRIVE OUT THE SLAVE WOMAN AND HER SON, FOR THE SON OF THE SLAVE WOMAN SHALL NOT BE AN HEIR WITH THE SON OF THE FREE WOMAN.” So then, brothers and sisters, we are not children of a slave woman, but of the free woman. (Galatians 4:28-31)

While we were still sinners, God made us His children through Jesus Christ. This eternal blessing was given free of charge. None of us kept the law perfectly. None of us knew the law. This is called the grace of God. Only those who received the Holy Spirit have the new heart to know and love God. The new heart is given not based on our works. Since God knew all of us before we were born, we conclude that the doctrine of divine election is a true doctrine. Those who rely on the law reject or will reject this doctrine. Most churches do not accept the doctrine. Even Reformed churches moved away from it because their foundation got shaken by the false doctrine called Active Obedience of Christ. The law is not our source of righteousness. Christ bought us to become God’s children. We are one with God through Jesus Christ and the Holy Spirit. This was done through Christ’s death on the cross.

But God demonstrates His own love toward us, in that while we were still sinners, Christ died for us. (Romans 5:8)