Exodus 24:7 And he took the book of the covenant, and read in the audience of the people: and they said, All that the Lord hath said will we do, and be obedient.
Moses took and read for the people the Book of the Covenant, Exodus 20-23. This included the Ten Words and much casuistry (“if that happens, then you do this”). The people responded to the reading of the Covenant with good and sincere intention: we will do what God says and we will be obedient. After God’s terrifying presence on the Mount (the Law) and God’s great salvation and miraculous deliverance (the Gospel), they responded with a resounding Amen, Yes, and a sincere promise to do and obey. They would fear and love God that they might….
The problem, of course, is that beings sinners they would never be able to do what God said nor keep their promise. They would fail, like all people, to keep their part of the covenant, thereby releasing God from the obligation to keep His Blessing part of the covenant. But One Man would enter and keep the covenant perfectly for all people, in our place, thereby obligating God to keep His Blessing for us.
We do well to make a promise to do and obey; however, we make a grave mistake if we think we will actually do it. The sinner cannot keep his promises, but thank God, Jesus can, and does, for us. Thus, the right response is faith in God’s conviction of sin and failure, and faith in God’s loving provision of forgiveness and salvation in Christ. Jesus keeps the promise. Jesus never fails.