How does Pharaoh know to summon Abram?

Question

In the first story about Abram after his calling, he goes down to Egypt because of a famine and Pharaoh takes Abram's wife Sarai into his household. As a result God inflicts Pharaoh with plagues.

But the Lord inflicted serious diseases on Pharaoh and his household because of Abram’s wife Sarai. So Pharaoh summoned Abram. "What have you done to me?" he said. "Why didn’t you tell me she was your wife?"

I realize the text is thin here, but how does Pharaoh know to summon Abram? Later in Genesis 20 when a similar even happens with Abimelek, God speaks to Abimelek in a dream to tell him he is a dead man. Abimelek protests he has a clean conscience. But nothing like that happens here. Should we infer in the Genesis 12 story that Pharaoh knew Sarai was Abram's wife, even if there was a charade among all parties to pretend otherwise?

Answer 1

The classical Jewish commentaries provide two answers to this question (and some combine them). The end of the 12:17 is not precisely translated in the question. The Hebrew עַל־דְּבַ֥ר שָׂרַ֖י אֵ֥שֶׁת אַבְרָֽם literally translates as "because of the thing (or incident) of Sarai the wife of Abram."

1. The affliction was one that made intercourse painful. Rashi citing Bereishit Rabba 41:2.

2. When secluded, Sarai told Pharaoh the truth but he did not believe her until the afflictions came. See Kli Yakar; Ohr HaChaim.

Radak combines the two, saying that Pharaoh first received the afflictions, leading him to question why they were occurring and he asked Sarai and she told him the truth.

Those commentators that say that Sarai told Pharaoh the truth are construing the text based on the use of the phrase עַל־דְּבַ֥ר שָׂרַ֖י instead of merely saying עַל שָׂרַ֖י (because of Sarai). The word דְּבַ֥ר can mean "statement" or "thing" or "incident."