The covenant, or treaty, that God made with Abraham involved obligations on both sides. God committed Himself to making Abraham the father of many nations and of giving the land of Canaan to him and his descendants for ever. Abraham and his descendants for their part were to oblige themselves to remain faithful to their God. They were not to abandon their God for other gods.
But they did! Time after time, throughout the centuries, the Israelites turned away from the God of their ancestors to worship pagan idols. In the process they inflicted on themselves sufferings, defeats and disasters before they would return to their true allegiance with God.
Jesus came to make a new covenant not just with the Israelites but with the whole world. In one sense it was an extension of the former covenant. "Your father Abraham rejoiced to think that he would see my day."
There were, however, important differences. The reward promised in the earlier covenant was ownership of the land: in the new covenant it was eternal life. Again, the obligation imposed by the new covenant is not just to avoid idol-worship, but "to keep my word". And the word of Jesus was to love God and to love one another.
It was because the Pharisees knew nothing of love that Jesus told them they did not know God. God is love.
Lord Jesus, give me the grace to keep Your word more faithfully by loving others as You have loved me.