All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah and that Muhammad is His slave and Messenger.
The books of Tafseer (exegesis) indicated what proves both views. Perhaps the more correct view is that Saarah (Sarah) was the cousin of Ibraaheem (Abraham) . It was also said that she was the daughter of the king of Harraan (Haran). These two views were mentioned by At-Tabari, but Ibn Katheer held the preponderant opinion that she was his cousin. At-Tabari said in his Tafseer:
As-Suddi narrated, “Ibraaheem and Loot (Lot) set off towards the Levant, and Ibraaheem met Saarah, who was the daughter of the king of Harraan, and she challenged her people about their religion, so he married her.”
Ibn Is-haaq narrated, “Ibraaheem migrated to his Lord, and Loot migrated with him as well, and Ibraaheem married Saarah, his cousin, so he migrated with her, fleeing with his religion in order to be safe in worshipping his Lord, until he settled in Harran...”
Besides, Tafsir Ibn Katheer (5/353) reads:
“As-Suddi said, Ibraaheem and Loot set off towards the Levant, so Ibraaheem met Saarah, the daughter of the king of Harraan, and she challenged her people about their religion, so he married her.
This was reported by Ibn Jareer, and it is a strange narration. The well-known view is that she was his cousin, and that he migrated from his country along with her.”
Allaah knows best.