Musar zu Bereschit 13:9

We find a clear allusion to this in 13,9 where Abraham says to Lot: "Is not the whole land before you, separate yourself from me; if to the Left, I will go to the Right, and if to the Right, I will go to the Left." The meaning of the verse is that Abraham asks Lot why he quarrels needlessly, seeing there will be a time when he will have the entire land to choose from and does not now need to take things before they are ripe. When would that time come? At the time the kingdom of David will be established, seeing that David is descended from Ruth. That same Ruth had said to her mother-in-law Naomi "only death will part us" (Ruth 1,17). Abraham meant the same thing when he spoke to Lot about הפרד נא מעלי, "please separate from me." According to Rabbi Yitzchak Arama in his commentary on Ruth, the latter made a very significant statement, namely that when members of the other nations die, that does not create a disparity among them because all of them proceed towards an eternal void. Since every Jewish person however has a share in the world to come, death creates a disparity amongst them, seeing their shares in that World To Come are not the same. Bamidbar Rabbah 21,22 comments that any bridegroom who is "greater" than his fellow-bridegroom will be burned by the fire G–d provides for the wedding canopy of the other, [a penalty for being envious of somebody else's status, see Baba Batra 75. The whole discussion is about G–d bestowing honor on the righteous in the world of the future. Ed.]. Thus we see that not everyone's share in the World To Come is equal. Hence the division between people will occur when they die and move to different parts of a new world.