What plans God has and why we cannot comprehend them unless it has been explained.
From the evidence we have available, there are some serious holes in the Isaac / Ishmael story, which I will come to later.
Generally
Polygamy was practiced widely at the time, especially if a wife was barren. Solomon even had 700 wives. There is nothing in the Bible that says polygamy is not allowed.
From the evidence there was a bad relationship between Hagar and Sarah – which many households would have understandably had due to human nature, jealousy, such as one wife being prettier, husband spending more time with one, heir going to the eldest child not necessarily the first wife, etc….
16:6 clarifies why Hagar initially left - “Your slave is in your hands,” Abram said. “Do with her whatever you think best.” Then Sarai mistreated Hagar; so she fled from her.
16:9 explains why Hagar went back, due to the commandment of God. God's plans cannot be questioned.
The main issue appears that Sarah didn’t want Ishmael to inherit their wealth as she now had a child so wanted to get rid of him so Isaac would be the only heir.
Regardless, God was clear that both were the seed of Abraham and will become great nations. This was not confirmed to Isaac only.
Genesis 16:3
So after Abram had been living in Canaan ten years, Sarai his wife took her Egyptian maidservant Hagar and gave her to her husband to be his wife.
Genesis 16:2
The Lord has kept me from having children. Go, sleep with my maidservant; perhaps I can build a family through her. Abraham agreed.
It is certain that Sarah and Abraham knew the law and did not want to waste their time during their old age building an illegitimate family that would serve them no good!
Genesis 22:16
I promise that I will give you as many descendants as there are stars in the sky or grains of sand along the seashore.
Genesis 17:20
As for Ishmael, I have heard you; behold, I have blessed him and will make him fruitful and multiply him greatly. He shall father twelve princes, and I will make him into a great nation.
Genesis 21:13
And also of the son of the bondwoman will I make a nation, because he is thy seed.
Genesis 21:20-21
20 And God was with the boy, and he grew up and settled in the wilderness and became a great archer. 21 And while he was dwelling in the wilderness of Paran, his mother got a wife for him from the land of Egypt.
The Problem with Genesis story
The story of Abraham and the great debate if it was Ishmael or Isaac who was the one that was going to be sacrificed will go on and on.
You would think God or his angel would know how many sons Abraham had.
Genesis 22:2
…Take now thy son, thine only son…”.
Genesis 22:12
your only son, from me
Genesis 17:19
I will establish My covenant with him as an everlasting covenant for his descendants after him.
How can Isaac have an ‘everlasting covenant for his descendants’ if he was going to be sacrificed? The first thing Abraham would say is, did you not promise Isaac 'descendants'.]
Genesis 25:9
Then his sons Isaac and Ishmael, buried him (Abraham) in the cave of Machpelah.
Clearly, they were still in touch – was there any grievance with them and who would be heir – see ‘rights of the firstborn’ below.
Genesis 21:14-15, 18
14 And Abraham rose up early in the morning, and took bread, and a bottle of water, and gave it unto Hagar, putting it on her shoulder, and the child, and sent her away: and she departed, and wandered in the wilderness of Beersheba. 15 When the water in the bottle was gone, she put the boy under a bush. ... 18 Come, lift up the boy and hold him fast with your hand, for I will make a great nation of him.”
Ishmael was approx. 14 when Sarah had Isaac (Genesis 16:16 / 21:5). Hagar left after Isaac was weened – so at least 3-4 years. In those days, someone aged 17/18 years old would be considered a man, he would be working probably in the field, and girls were married by 14 years.
He would have carried the food & water, the Hebrew suggests Hagar also carried the boy on her shoulder (the Hebrew translation 21:14 says ‘putting [it] on her shoulder and the boy).
Genesis 21:15, how can Hagar ‘put the boy under a bush’, he was probably bigger than her
Genesis 21:18, how can she pick the boy up, in Genesis 21:21 he is getting married.
Is he a little child?
Some prophecies of Ishmael's descendants
Isaiah 42:11-15
11 Let the wilderness and its towns raise their voices; let the settlements where Kedar lives rejoice. Let the people of Sela sing for joy; let them shout from the mountaintops. 12 Let them give glory to the LORD and proclaim his praise in the islands. 13 The LORD will march out like a champion, like a warrior he will stir up his zeal; with a shout he will raise the battle cry and will triumph over his enemies.
And when they give the book to one who cannot read, saying, ‘Read this,’ he says, ‘I cannot read.’” “For with stammering lips and another tongue will he speak to this people.” (Isaiah 28:11)
Isaiah 29:12
And when they give the book to one who cannot read, saying, ‘Read this,’ he says, ‘I cannot read.’”
Isaiah 28:11
Nay, but by men of strange lips and with another tongue will he speak to this people;
Strange / another tongue would indicate a different language, ie Arabic as Arabs are the descendants of Ishmael and have multiplied
Right of the Firstborn
Deuteronomy 21:15-17
The Right of the Firstborn
15 If a man has two wives, and he loves one but not the other, and both bear him sons but the firstborn is the son of the wife he does not love, 16 when he wills his property to his sons, he must not give the rights of the firstborn to the son of the wife he loves in preference to his actual firstborn, the son of the wife he does not love. 17 He must acknowledge the son of his unloved wife as the firstborn by giving him a double share of all he has. That son is the first sign of his father’s strength. The right of the firstborn belongs to him.
Many disregard Ishmael as Hagar was a servant/handmaid and that. Then you have to be consistent and you face 2 major problems.
Jacob & his four wives - Children of Handmaids
Jacob had four wives and 12 children that make up the Israelites. All accepted and referred to as a combined group.
Genesis 30:4 two of the wives are slave-girls Zilpah & Bilhah (šip̄·ḥā·ṯāh שִׁפְחָתָ֖הּ her maidservant) Four of the twelve children Gad, Dan, Naphtali and Asher were there sons.
The Bible tracks all their genealogy in (1 Chronicles 5:18; 1 Chronicles 7:12, 13, 30), none are differentiated.
1 Chronicles 7:40
All these were descendants of Asher, heads of families, picked men of ability, leading princes.
Should a 1/3 of the Israelites accept that they are illegitimate?
Abraham’s children (Hagar, Sarah & Keturah) are also traced in 1 Chronicles.
Ruth 1-4
She was also a maidservant/handmaid as was Hagar.
The story itself raises numerous issues including illegitimate sexual relationships, laying at one’s feet is understood to be sleeping with them, But putting that to one side & there is no indication in Leviticus that redemption of a kinsman’s property is in any way connected to marriage with the kinsman’s widow.
Ruth was a young widow and a handmaid of Moabite descent.
Moabite people were descendants of an act of incest by Lot and his daughters (Genesis 19:36-37)
Boaz was old and must have had other wives/maidservants – but everyone seems to die conveniently to leave a clear legacy.
Boaz is not Ruth’s brother-in-law, nor does the genealogy in Ruth 4 credit Ruth’s son to her deceased husband’s line.
Son Obed – who became the Royal line of Israel – ancestor to Kind David and Jesus
Why is her lineage not questioned?
Conclusion
Clear evidence of human additions, deletions, and interpolations. The intention is to show that Hagar was not Abraham’s wife, a handmaid, Ishmael was an illegitimate child of a bondmaid, and Sarah a free woman. Isaac was a promise and unique and the new grace convent and Hagar was the old bondage convent. So, the family of Isaac will inherit.
All this is just a ‘biased’ interpretation to disregard the Ishmael lineage and the Arabs by the Israelites as the promise of the future messiahs/prophets as far as the Israelites are cornered are from the Issac lineage, the Christians are happy to play the part to argue the lineage of Jesus (can Jesus really be the seed of Abraham when Jesus has no father, it never goes by the mother?).
Jacob's children all respected the same, regardless of the wife’s status.
Pure inconsistency due to bias
Final note
Jeremiah 8:8
How can you say, we are wise, since we have Yahweh’s Law? Look how it has been falsified by the lying pen of the scribes.