I don't know how much time had passed between the promise of children to Abram and Sarai in chapter 15 and the scheme hatched by them to take matters into their own hands in chapter 16. What I notice in this chapter is this cascading waterfall of doubt, sin, and destruction that spirals out from Sarai and Abram. In the Bible, the name for pretending to be a false god is injustice, and I notice that process play out in this story.