"So he went in to Hagar, and she conceived. And when she saw that she had conceived, her mistress became despised in her eyes. Then Sarai said to Abram, 'My wrong be upon you! I gave my maid into your embrace; and when she saw that she had conceived, I became despised in her eyes. The LORD judge between you and me.' So Abram said to Sarai, 'Indeed your maid is in your hand; do to her as you please.' And when Sarai dealt harshly with her, she fled from her presence" (Gen. 16:4-6). It didn't take long at all for Hagar to get pregnant. There is a falling out between the two women, as might be expected in such an emotional situation. Hagar, who easily became pregnant, feels superior to Sarai--and shows it. Sarai becomes bitter about the situation and treats her maid harshly. The woman carrying Abram's child flees her home. Abram does nothing to stop her, perhaps realizing the foolishness of what had been done and not wanting to further agitate Sarai. One cannot fault Abram or Sarai here for lacking faith, though their "solution" to what they deemed to be a problem (their age) was not what God had in mind at all. He intended to give Abram and Sarai a son of their own, but they needed to wait approximately 15 more years! The time was not yet ready, though they are ready now and attempt to "help" God along. Interestingly enough, it is often difficult to assess the long-term consequences of our actions. Abram's attempt to "help" God resulted in creating a race of people who to this day have been at enmity with Abram's descendants. Mohammed traced his lineage through Ishmael! How much human misery and confusion might have been avoided had Abram refused to heed the voice of Sarai (cf. Gen. 3:6).
"Now the Angel of the LORD found her by a spring of water in the wilderness, by the spring on the way to Shur. And He said, 'Hagar, Sarai's maid, where have you come from, and where are you going?' She said, 'I am fleeing from the presence of my mistress Sarai.' The Angel of the LORD said to her, 'Return to your mistress, and submit yourself under her hand.' Then the Angel of the LORD said to her, 'I will multiply your descendants exceedingly, so that they shall not be counted for multitude'" (Gen. 16:7-10).
Hagar was making her way back to Egypt, but God intervened and instructed her to return to Sarai. God promised Hagar that the son she was carrying in her womb would have numerous descendants. Hagar obeyed.
"And the Angel of the LORD said to her: 'Behold, you are with child, and you shall bear a son. You shall call his name Ishmael, because the LORD has heard your affliction. He shall be a wild man; his hand shall be against every man, and every man's hand against him. And he shall dwell in the presence of his brethren'" (Gen. 16:11,12). Ishmael would be a wild man, not a peace maker, but he wouldn't be a slave. Hagar then calls the LORD "the-God-Who-Sees." The chapter closes with Ishmael's birth. Abram was 86 years old! It is likely that Abram did view Ishmael as the promised son at this time. He would learn otherwise later.