It's the same situation in Exodus 32:7 - 14. God is disowning his people. He says to Moses, "Go down at once to your people, whom you brought out of the land of Egypt." They are no longer His people, whom He brought out of Egypt. No. Now they belong to Moses because after all God has done for them, they have created an idol for themselves and claimed it as their God. He even goes on to say, "Let me destroy them and then I will make you a great nation." Whoa.
Moses, smart man that he is, picks up on this. He quickly reminds God that they are His people; He brought them out of Egypt; and He promised to make the descendants of Abraham into a great nation. He's not going back on his word, is He?
And so God relents of the threatened punishment, so rightly deserved. Once again, God shows mercy in the face of gross disobedience. He keeps faith with a faithless people.
For Reflection: Is there reason to disown us? Do we remember what God has done for us? Can we recall the promises He has made to us that have yet to be fulfilled? Are we able to count how many times God has shown us mercy?