Abraham will surely become a great and powerful nation, and all nations on earth will be blessed through him

 Genesis 18:17-33

When the men got up to leave, they looked down toward Sodom, and Abraham walked along with them to see them on their way. Then the Lord said, “Shall I hide from Abraham what I am about to do? Abraham will surely become a great and powerful nation, and all nations on earth will be blessed through him. For I have chosen him, so that he will direct his children and his household after him to keep the way of the Lord by doing what is right and just, so that the Lord will bring about for Abraham what he has promised him.”

Then the Lord said, “The outcry against Sodom and Gomorrah is so great and their sin so grievous that I will go down and see if what they have done is as bad as the outcry that has reached me. If not, I will know.”

The Lord said, “If I find fifty righteous people in the city of Sodom, I will spare the whole place for their sake.”...

Then he said, “May the Lord not be angry, but let me speak just once more. What if only ten can be found there?” He answered, “For the sake of ten, I will not destroy it.” 

When the Lord had finished speaking with Abraham, he left, and Abraham returned home.

Why?

The sins of Sodom were severe, and almost no one was a righteous man. So the Lord was angry and ready to destroy this city. After Abram 5 time begged the Lord, if there were ten righteous men, the Lord wouldn't destroy this city. But only Rot was a half-righteous man. 

God is full of mercy when the whole land is full of sins, which means the end of this land. So same as the men in this world.

How?

Because the Lord is righteous so sinners could not stand before the Lord. Christians can face the Lord because of the salvation of Jesus Christ, who open a new way for all of us.