Exodus 19:8 And all the people answered together, and said, All that the Lord has spoken we will do. And Moses returned the words of the people unto the Lord.
The people responded to God’s great salvation and awesome presence by making a vow and a promise. The Lord had just said: ”If you obey My voice and keep my covenant I will make you a peculiar treasure, a kingdom of priests, and a holy nation.” They responded to these words with a vow, ”We will do.” They were also committing themselves to keeping the Ten Words that the Lord would soon speak and write to Moses.
Of course, they could not do the words nor keep their promise. The Lord had frightened and loved them into responding with a vow they could not and would not keep. Almost immediately, they worshiped the golden calf, evidencing their broken promise.
However, the fact that we cannot keep our vows should not prevent us from making promises to do better. Daily repentance and faith is necessary for believing sinners. Repeated failures call for repeated godly sorrow before God’s Law, and reinforced genuine faith in God’s Gospel. This process, produced by fear and love of God, over time sanctifies us through Word and Spirit. We don’t give up on God because we failed, for God does not give up on because Jesus never fails.