In those days a married woman who had no children suffered contempt by the others. To overcome this problem, she would deliver one of her servants to her husband to replace her, and according to legal codes and marriage contracts of that time, their offspring were considered as children of the wife.
Although what Sarai and Abram did was a legal action in the world of their time, it did not have God’s approval. Sarai, who was 75 years old, was the one who had taken the initiative, certainly not understanding that the son God had promised to Abraham would come from her (17:15-16). They erred in not awaiting patiently the time when God would act to fulfil His promise, and consequently they and their descendants would suffer problems.
When she found she was pregnant, Hagar began to despise Sarai, and Sarai, now recognizing the mistake she had made, blamed Abram although the initiative had been her own (it is common for people to try to transfer their blame to others).
As Abram had returned Hagar to Sarai, she apparently became her slave again and lost any privilege she had enjoyed before; Sarai took advantage of her legal rights to humiliate her to the point that Hagar could no longer bear it and fled into the desert. She followed the way to Sur, a road that stretched from Beersheba to Egypt, her homeland.
There she had an encounter with the angel of the LORD: this is the first time that this character is mentioned, being a visible manifestation of God. He is mentioned many times in the Old Testament (see also Genesis 21:17-21, 22:11-18, 31:11-13, Exodus 3:2, Judges 2:1-4, 5:23, 6:11 - 14, 13:3-22, 2 Samuel 24:16, Zechariah 1:12, 3:1, 12:8) and never in the New Testament, indicating that this is the second person of the Trinity.
The Angel of the LORD mercifully told Hagar to return immediately to her mistress and submit to her. He furthermore blessed Hagar with the promise of a son whom she should call of Ishmael (God hears), and a great descent, an independent people like a wild ass: an almost indomitable animal, which was much admired and valued. The rest of verse 12 means that the descendants of Ishmael would live east of the other descendants of Abraham, or that they would live in constant defiance against them.
The well of Beerlahairoi (well of a living (One) my Seer) would probably be southwest of Beersheba, but the exact location is unknown because it has not survived to this day through the millennia.
Hagar was obedient and went back to her mistress. In due course she gave birth to her son, who Abram called Ishmael, as God had commanded.
In his Epistle to the Galatians (some Jewish believers in Galatia wanted to bring under Jewish law the newly converted Gentiles), the apostle Paul uses the episode of Hagar as an allegory of the law of Moses (4:21-31): the slave Hagar corresponds Mount Sinai, which generates the son Ishmael for slavery, symbolizing law; Sarai, Abram's wife, corresponds to the heavenly Jerusalem, and his son Isaac, a freeman, is the son of promise as well as all believers in Christ.
This is the fifth test out of a total of seven to which Abram was submitted:
Test of dedication: God called Abraham to leave his land and his relatives in Ur of the Chaldeans, and Abram obeyed in part because his faith was still immature. He did relatively well.
Test of perseverance: When there was famine in the land where he was living, Abraham fled to Egypt. There he acquired wealth and Hagar - two obstacles he would have to face later. He failed this test.
Test of comfort: Because of his wealth he finally separated himself from Lot, but showed selflessness and risked everything when He rescued Lot. Passed.
Test of godliness: winning the battle against the kings of the east, he humbled himself before Melchizedek, the priest, and refused the spoil that the king of Sodom offered him. Passed.
Test of patience: given the delay in receiving the heir that God had promised him, Abram succumbed to his wife’s impatience and begat a son from the slave Hagar. The consequences are being suffered right until today through the enmity and frequent fighting between Arabs and Jews, which will continue until the millennium. Failed.
Test of brotherly love, before the destruction of Sodom and Gomorrah (Chapter 18). Passed.
Test of faith: willingness to sacrifice his son Isaac upon God´s command (chapter 22). Passed.
1 Now Sarai, Abram's wife, had borne him no children. And she had an Egyptian maidservant whose name was Hagar.
2 So Sarai said to Abram, "See now, the LORD has restrained me from bearing children. Please, go in to my maid; perhaps I shall obtain children by her." And Abram heeded the voice of Sarai.
3 Then Sarai, Abram's wife, took Hagar her maid, the Egyptian, and gave her to her husband Abram to be his wife, after Abram had dwelt ten years in the land of Canaan.
4 So he went in to Hagar, and she conceived. And when she saw that she had conceived, her mistress became despised in her eyes.
5 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."
6 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.
7 Now the Angel of the LORD found her by a spring of water in the wilderness, by the spring on the way to Shur.
8 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."
9 The Angel of the LORD said to her, "Return to your mistress, and submit yourself under her hand."
10 Then the Angel of the LORD said to her, "I will multiply your descendants exceedingly, so that they shall not be counted for multitude."
11 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.
12 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 all his brethren."
13 Then she called the name of the LORD who spoke to her, You-Are- the-God-Who-Sees; for she said, "Have I also here seen Him who sees me?"
14 Therefore the well was called Beer Lahai Roi; observe, it is between Kadesh and Bered.
15 So Hagar bore Abram a son; and Abram named his son, whom Hagar bore, Ishmael.
16 Abram was eighty-six years old when Hagar bore Ishmael to Abram.
Genesis chapter 16