“Therefore choose life, that you and your offspring may live, loving the Lord your God, obeying his voice and holding fast to him, for he is your life and length of days, that you may dwell in the land that the Lord swore to your fathers, to Abraham, to Isaac, and to Jacob, to give them.” (Deuteronomy 30:19b-20)
The Lord offered the Israelites a choice: serve Him and be blessed or abandon Him and perish. Even if they pledged to serve Him and walk in obedience now they would still have to understand the consequences for any future apostasy. If and when they lapsed into idolatry and apostasy the people would be punished. Yet the punishment was always designed to bring them back to Him. Yahweh promised that there was always a way back. He would restore their blessings if they repented of idolatry and walked again in obedience. After all, He loved them and cared for them.
The commands the Lord gave the Israelites proved to be impossible to follow due to the corruption of the flesh. But the Israelites did not think so. They committed the same sin all humans commit: they thought that perfect obedience was possible without any help from God. It is not. What is required is a circumcised heart. Physical circumcision was the outward sign that one belonged to the descendants of Abraham but did not guarantee that one was really committed to the Lord or even acceptable in His sight. Inward circumcision is the sign that marks all true believers. It is a heart that is humble and weak, one that has faith in Christ not in self or the world. Believers realize that they are sinners who are incapable of obedience. They throw themselves on God’s mercy. He them enables them to obey and to live as members of His kingdom.