פּירוש אויף דברים 9:29

והם עמך ונחלתך, “seeing that they (the Jewish people) are Your people and Your inheritance.” Moses was forced to remind G–d of this as G–d had said to him before He commanded him to go down from Mount Sinai with the two Tablets שחת עמך, “your people have become corrupted.” (Exodus 32,7)

Your people and Your inheritance because of their forefathers.

והם עמך ונחלתך, “seeing that they are Your people and Your inheritance.” Moses means that “You” employed these two attributes when You took them out of Egypt. If You do not forgive them, the Egyptians will interpret this as inability on Your part to carry out Your plan. They will retroactively lose all the respect they gained for You as a result of the miracles You performed for the Jewish people.