Promise

Hashem made Avraham a series of promises. These were that he would have so many future generations that he would not be able to count them, Avraham would be given all the land and after him his children would inherit it after him, material wealth, anyone who curses him will be cursed and anyone who blesses him will be blessed, and lastly he will be a bracha to everyone. After Hashem gives him these promises, Hashem brings him, his wife Sarai, and lot to Egypt due to a famine. Avraham has to leave his homeland and follow G-d. Avraham of course follows. When they get there, they pretend that Sarai is really Avraham's sister rather than his wife, to safe his own life. Pharaoh takes Sarai as a wife only to find out later that she is really Avraham's wife. Pharaoh throws him in jail but miraculously send him out on the condition that he leaves Egypt. From this we learn how immoral Egyptians are. They were willing to kill Avraham just because he was married to a beautiful woman whom they wanted. Avraham, Sarai, and Lot take their belongings and their wealthy and leave Egypt. The only problem is that Lot was very influenced by the immoral ways of the Egyptians that he decided to go live in a city that was like it. Avraham on the other hand, uninfluenced by Egypt decides to keep going on his path like he was before, going in the name of G-d. Hashem though, must sense a feeling of uneasiness from Avraham because He feels the need to repeat the promises to him again. This could be because Avraham might have thought that he was already 75 and he could not have children anymore, thus making Lot his only descendent. Now that Lot chose this "bad" city though, Avraham could have been worried that he would not have any future generations. Hashem comes to the rescue and reassures Avraham that he will have future generations who will be as great as the dust of the land. Hashem also tells Avraham to look at all the land from one side of the world to the other. This is probably because Avraham might have felt that he would not get all the land because Lot just chose this bad city. Hashem thankfully steps in and reassures Avraham, calming all his nerves.