- Egypt at that time was the world center of occult, it was home to the most advanced sorcerers and magicians.
- Paroh had viewed in his horoscope that he was destined to intermarry into Avrahoms family. This is one of the reasons he wanted to marry Sarah whom he thought was Avrahoms sister.
- After he realized Sarah was really his wife, he gave Avrahom his daughter Hagar as a maid servent. Secretly he hoped Avrahom would marry her as predicted in his horroscope.
- Paroh had his sorcerers cast spells on Sarah preventing her from having children.
- Sarah realized this was part of the reason she was unable to give birth.
- She therefore gave Hagar to Avrahom to marry. For when the condition for the magic was fulfilled the spells would break.
- An additional reason is the following:
-Avrahom still had a lot of zuhamah in him from Terach.
- Sarah did not want this passed over to her child she therefore gave him Hagar so her son would absorb most of the impuity.
- Once the impurity was passed on she was then able to have a son from Avraham.

(R’Yonason Tifferet Yonason)