With this verse, Moses attempts to convince God to spare the Jewish nation, despite the egregious sin of the golden calf. He pleads with God to remember his oath to Abraham, Isaac and Jacob that their progeny will inherit the land of Israel.
Moses is concerned that if God is to destroy the Nation and re-create a great nation from him alone, the promise of the Holy Land made to the Patriarchs would be lost. He therefore pleads with God to spare the people despite their transgressions.