There were a number of interesting takes that I've read so far, but I now felt compelled to write about one of the pieces on Lech Lecha because it comes so close to what I wrote in this blog on a different parsha: http://kallahmagazine.blogspot.com/2017/12/when-star-dies.html.
In 15:5, Avram is assured that he will not remain childless:
And He took him outside, and He said, "Please look heavenward and count the stars, if you are able to count them." And He said to him, "So will be your seed."הוַיּוֹצֵ֨א אֹת֜וֹ הַח֗וּצָה וַיֹּ֨אמֶר֙ הַבֶּט־נָ֣א הַשָּׁמַ֔יְמָה וּסְפֹר֙ הַכּ֣וֹכָבִ֔ים אִם־תּוּכַ֖ל לִסְפֹּ֣ר אֹתָ֑ם וַיֹּ֣אמֶר ל֔וֹ כֹּ֥ה יִֽהְיֶ֖ה זַרְעֶֽךָ:
Rav Schwab says that the simple meaning indicates that this refers to all the offspring of Avraham in the course of all the generations together will be like the stars, though after this , it becomes cle…