When God gave the Ten Commandments at Mount Sinai, the sages taught that He did not speak them into a void. Each commandment was connected to the covenant God had already made with Abraham — the covenant of circumcision, the covenant of the land, the covenant of descendants as numerous as the stars.
The Midrash (Pesikta Rabbati 23) traces each of the ten utterances back to a moment in Abraham's life. "I am the Lord your God" — this echoed the first time God spoke to Abraham: "Go forth from your land" (Genesis 12:1). "You shall have no other gods" — this recalled Abraham smashing his father's idols. "Remember the Sabbath" — this connected to Abraham's hospitality, for he rested from nothing in his service of others.
The message was clear: the Torah at Sinai was not a new beginning. It was a continuation. Every commandment the Israelites received had already been lived by their ancestor. Abraham kept the Sabbath before it was commanded. He honored his parents — after his own fashion — before it was law. He refused to steal when the King of Sodom offered him spoils.
The sages drew a profound conclusion. The Decalogue was not imposed on Israel from above. It was drawn out from what Abraham had already planted in the Jewish soul. The covenant at Sinai merely made explicit what the Abrahamic covenant had always contained. The children inherited what the father had earned.