They may enter and possess the land I swore to their ancestors to give them

Deuteronomy 9:17-10:11

I feared the anger and wrath of the Lord, for he was angry enough with you to destroy you. But again the Lord listened to me. And the Lord was angry enough with Aaron to destroy him, but at that time I prayed for Aaron too.

You also made the Lord angry at Taberah, at Massah and at Kibroth Hattaavah.

So I made the ark out of acacia wood and chiseled out two stone tablets like the first ones, and I went up on the mountain with the two tablets in my hands. The Lord wrote on these tablets what he had written before, the Ten Commandments he had proclaimed to you on the mountain, out of the fire, on the day of the assembly. And the Lord gave them to me. Then I came back down the mountain and put the tablets in the ark I had made, as the Lord commanded me, and they are there now.

That is why the Levites have no share or inheritance among their fellow Israelites; the Lord is their inheritance, as the Lord your God told them.) Now I had stayed on the mountain forty days and forty nights, as I did the first time, and the Lord listened to me at this time also. It was not his will to destroy you.  “Go,” the Lord said to me, “and lead the people on their way, so that they may enter and possess the land I swore to their ancestors to give them.”

But if they will let it, the past can keep them on the right lines for the future.

Why?

Moses reminded them how they have done rebellion against the Lord.

For Moses pleased the Lord and the Lord remember the covenant with their ancestors so God allow them survived and asked Moses to bring them into the promised land on the way. 

How?

Great is the Lord, for his love and righteousness endure forever.