What does "Vayish'alu... l'Ishto" mean?
Rashi: It means (not that they asked his wife, rather,) 'they asked about his wife.' 1
Ha'amek Davar: They asked (Malbim - also) his wife.
Rashi: As above, 20:13.
Why, when Yitzchak told them that Rivkah was his sister, did they not question him about the children (Yaakov and Esav)?
Ramban: Because, as far as they were concerned, they may well have been somebody else's children. 1
They could even have been his sister's or his own children.
Why was he afraid lest they kill him due to Rivkah?
Malbim: He suspected everyone, because [all] "Anshei ha'Makom" asked about her, and they also asked her herself.
Why didn't Yitzchak tell her to say that she is his sister, like Avraham told Sarah?
Ha'amek Davar: He did not need to, for she was exceedingly reverent of Yitzchak, and would never do anything against his desire, as explained above (refer to 24:62:1:7*).
Why was Yitzchak afraid? HaSh-m had told him, "v'Ehyeh Imcha" (26:3)?