One of the teachers of the law came and heard Jesus arguing with the Sadducees. Seeing that Jesus gave good answers to their questions, he asked Jesus, “Which of the commands is most important?”
They were asking this to trick Jesus so that they could have some charge against him. But Jesus bent over and started writing on the ground with his finger.
If the law could give us Abraham’s blessing, then the promise would not be necessary. But that is not possible, because God freely gave his blessings to Abraham through the promise he had made.