So it came to pass that God impregnated Sarah. I mean, Abraham impregnated Sarah. Yah, that’s the ticket.
Anyway, however it happened, Sarah had a son. Feeling somewhat roped into God’s suggestion because of the whole Miracle Birth thing, Abraham named the son Isaac, even though he had been secretly hoping his first legitimate son would be called Bluto.
Abraham then lopped off part of “Little Isaac” in deference to God’s command, and then gave the baby to Sarah to breastfeed. Given that Sarah was an old crone by this point, she likely was giving Isaac powdered milk. At any rate, she managed to keep the kid alive until he could be weaned, and Abraham threw a party because of it.
Sarah saw Hagar, who was busy minding her own business, and decided to heckle her for daring to have Abraham’s illegitimate son, even though Sarah herself had told Hagar to do so. Sarah heckled Hagar so much that she felt compelled to leave, and took off with her son Ishmael for greener pastures.
Unfortunately for her they were in the Middle East, and there were no greener pastures for hundreds of miles. She wandered around for a while until she ran out of water, and eventually gave up. Since she assumed her and her child were about to die, she did the logical thing and dumped the baby in a bush so she wouldn’t have to actually see him kick the bucket.
Fortunately for Hagar, God decided life would be boring without Muslims and decided to save Ishmael. So, God moved some branches out of the way and showed Hagar a well, and thus Ishmael was saved. God took Ishmael under his wing and taught him to be an archer, which would come in handy when God demanded Ishmael sacrifice all those sheep later on.
It came to pass that Abimelech (Remember him? The sucker who couldn’t get it up for Sarah earlier?) found Abraham still hanging out on his land, and begged Abraham not to lie to him again. Abraham agreed, but then started bitching about a well that he had been using until some of Abimelech’s people had decided to take it away from him. So, to recap, Abimelech gave Abraham a bunch of shit so he would stop trying to get Abimelech cursed by God, and instead of being happy with what he got, Abraham starts bitching about a well. Right on, Abraham.
Anyway, Abimelech promised to dig another well for Abraham in exchange for some sheep. Since the well’s water was of high enough quality to use in the brewing of some choice booze, the land it was on was called Beersheba.