[I]f the Abrahamic covenant contained the promise of redemption, why was another covenant formed at Sinai? In their bondage the people had to a great extent lost the knowledge of God and of the principles of the Abrahamic covenant. In delivering them from Egypt, God sought to reveal to them His power and His mercy, that they might be led to love and trust Him. He brought them down to the Red Sea—where, pursued by the Egyptians, escape seemed impossible—that they might realize their utter helplessness, their need of divine aid; and then He wrought deliverance for them. Thus they were filled with love and gratitude to God and with confidence in His power to help them. He had bound them to Himself as their deliverer from temporal bondage.
But there was a still greater truth to be impressed upon their minds. Living in the midst of idolatry and corruption, they had no true conception of the holiness of God, of the exceeding sinfulness of their own hearts, their utter inability, in themselves, to render obedience to God’s law, and their need of a Saviour. All this they must be taught.