Ten years into the land, still no child, and Sarai proposes the workaround: give Abram her slave Hagar, let the promised heir come by proxy. Watch the language carefully — Abram "hearkened to the voice of" Sarai, which is nearly the identical phrase used of Adam hearkening to the voice of Eve in chapter three. That's not incidental. It's the narrator marking this as a fall pattern: when the promise is slow, the flesh proposes a shortcut, and the man goes along with it.
What actually happens to Hagar deserves to be named plainly — a powerful couple use a foreign slave woman's body to solve their own problem, and she has no say in it. And then watch what God does, because it's the real center of the chapter: He goes after the slave, not the patriarch. The Angel of the LORD finds her at a spring and calls her by name — the only person in this whole narrative God addresses by name out in the wilderness — and gives her a promise that echoes Abram's own. She responds by doing something no one else in Scripture has yet done: she names God. El Roi — "the God who sees me." The first person to name God in the Bible is not a patriarch or a priest. It's a used, discarded, foreign slave woman, alone in the desert. Mogobe Ramose and Chabani Manganyi would both press on this: Hagar is defined throughout by her body — her fertility used, her affliction seen — and it is precisely her body, her affliction, that God sees. That's not a footnote to the covenant story. It's the covenant God's character on display before the covenant line is even finished being established.
Paul, much later, will use Hagar and Sarah as an explicit allegory in Galatians four — Hagar representing the covenant of slavery and law, Sarah the covenant of promise and freedom. He tells you himself that's what he's doing; it's a theological reading laid over the story, not the story's own plain sympathy for a wronged woman. Keep those two readings distinct and hold them both — Paul's allegory doesn't cancel Genesis sixteen's own compassion.