"After this the word of the Lord came to Abraham in a vision: 'Do not be afraid, Abraham. I am your shield, your very great reward.' But Abraham said, 'O Sovereign Lord, what can you give me since I remain childless? Now I am about to die and a servant in my household will be my heir.'" (Gen. 15,1-4). An obvious problem for the newly-elected prince was how to procure a legal heir; in spite of all efforts, "Sarah, wife of Abraham, had not been able to give him children. But she had an Egyptian slave-girl named Hagar, so Sarah said to Abraham, 'The Lord has kept me from having children. Go, sleep with my maid servant; perhaps I can build a family through her.' Abraham accepted her suggestion. When Sarah gave her husband the slave-girl, Hagar the Egyptian, they had been living in the land of Canaan for ten years." The campaign against the four rebel princes had just ended.
Who was this Hagar? The term "slave" is certainly not appropriate. The marriage customs and questions of hereditary rights in the Egyptian Empire at the time of the 18th Dynasty are well-known. The Pharaoh had dozens of wives who were normally upper class, although this was not always the case. The rank of the Pharaoh's offspring depended on the status of the mother; the son of a slave stayed at slave level. Pharoah's legal heir was the first born son of the highest-ranking wife, usually a sister, or even a daughter of the Pharaoh. If this wife failed to produce a son, a problem arose since it became necessary to unequivocally establish which of the secondary wives was of the highest rank. In that case, as it was for Tuthmosis III and his grandson, Tuthmosis IV, the choice was decided by the oracle.
According to Genesis, the Patriarchs' marriage and heredity customs were both completely the same. Abraham had several wives and children, but expected the legal heir from Sarah; Lot had legal heirs from an incestuous relationship with his two daughters; Isaac married his second cousin Rebekah, Jacob two of his first cousins, and so on. Abraham had no sons by Sarah, so his heritage would have gone to a son by one of his secondary wives: a “servant”, since this one was the son of a woman not from a ruling family. The fact that Hagar was given to him in order to produce a legal heir presupposes that she was not a common servant but a woman of upper class lineage. The rest of the account confirms this conclusion. Hagar's behavior, looking down on the "princess" Sarah, would be inconceivable coming from a lowly servant. Nor is it conceivable that Sarah should have to ask Abraham's permission to put down one of her own slaves. Also, when Hagar fled, resentful of the ill treatment she had received from Sarah, it was "an angel of the Lord", that is, a high-ranking person of the Egyptian hierarchy, who induced her to return to her mistress. Again, before throwing her out permanently together with her son Ishmael, Abraham requested the authorization of a person much higher than himself, to whom he turned and addressed as "Elohim" (Gen. 21,12), a name which we have seen was used only for the Pharaoh. This person was pleased to give his authorization, and assured Abraham that he would personally provide for the boy's future; it was in fact he who "saved" Hagar in the desert and made Ishmael a prince, assigning him a territory in the "Desert of Paran" (Gen. 21,21). A prerogative such as this could come only from the Pharaoh.
The inevitable conclusion is that Hagar was under the protection of Tuthmosis the Third. We can even deduce that she was his daughter from Genesis 15, in which Yahweh (that is, the Pharaoh) in response to Abraham's protest, declared, "This man will not be your heir but a son coming from your own body will be your heir." This verse has almost certainly been retouched to alter the meaning completely; originally it should have been, "This man will not be your heir, but a son coming from “my” own body will be your heir."
Tuthmosis was not omnipotent and certainly not able to guarantee Abraham that he could cure Sarah's sterility, and she was the only woman who could bear a male heir as required by the dynastic custom of the time. He could, however, give Abraham a wife of sufficiently high level to ensure progeny of noble blood and of whom no one could have any doubts, since they would be descendants of Pharaoh's seed, i.e. from one of his daughters.
This appears by no means unlikely; Tuthmosis had dozens of concubines and during his lifetime he probably fathered a very large number of children. Obviously he had to provide for their future in as dignified a manner as possible. The various temples scattered throughout Egypt were an almost inexhaustible resource for this; but it cannot be excluded that a certain number of his children were provided for differently, in some cases to his great political advantage.
Abraham was the son of a great emperor of the period, second only to the Pharaoh; he was a prince of the Egyptian Empire, therefore, he was by no means a bad match even for a Pharaoh's daughter. Also, in this way the Pharaoh was able to achieve a dual objective: set up his daughter in a satisfactory manner and guarantee the allegiance of his newly-sworn feudal lord, binding the latter to him through kinship and repaying the debt owed to Abraham for faithfulness and courage shown in the recent military campaign.
Genesis itself in fact loosely links Yahweh's promise to the victorious conclusion of the campaign against the Syrian rebel princes, by: "Your recompense will be very great," he assured Abraham--a promise which was kept by the birth of Ishmael, an heir born of Yahweh's seed. Tuthmosis wiped out his debt to Abraham by giving him a wife--his daughter Hagar--who arrives on the scene just at the conclusion of the military campaign.
In Genesis, Hagar is described as a servant of Sarah, but in reality she must have been one of Abraham's true and proper wives. The term "servant" merely indicates that she was a secondary wife, therefore, subordinate to his principal wife, Sarah. Obviously, the fact that Hagar could be a daughter of Yahweh must have seemed inconceivable to the compiler, who identified Yahweh with the Divinity, and, therefore, he "corrected" the text to suit himself.
When Hagar became pregnant and began to give Sarah looks of contempt, Sarah said to Abraham, "You are responsible for the wrong I am suffering. I put my servant in your arms and now that she knows she is pregnant she despises me. May the Lord judge between you and me." Obviously Sarah did not dare ill-treat the girl, as she would have done with any normal servant. Instead she pleaded for Pharaoh's judgement and explicit permission from Abraham, who replied, "'Your servant is yours; do with her whatever you think best.' Then Sarah ill-treated Hagar; so she fled from her. The angel of the Lord found Hagar near a spring in the desert; it was the spring that is beside the road of Shur. So he said, 'Hagar, servant of Sarah, where have you come from and where are you going?' 'I am running away from my mistress Sarah,' she answered. Then the angel of the Lord told her, 'Go back to your mistress and submit to her (...).' So Hagar bore Abraham a son and Abraham gave the name Ishmael to the son she had borne. Abraham was 86 years old when Hagar bore him Ishmael" (Gen. 16,7-16).