1) Rashi writes (18:2) that one of the three angels was sent to heal Avraham from the pain of his bris milah. The Gemara in Bava Basra (16b) teaches that Avraham wore a precious stone around his neck that had the ability to heal any sick person who looked at it. Why did Hashem send an angel to heal Avraham when he could heal himself by gazing at this stone?
2) Rashi writes (Bereishis 18:9) that the angels asked Avraham where Sorah was to send her the kos shel berachah, cup of wine used for birchas hamazon. Rashi writes (18:8) that although Avraham asked Sorah to make bread, it wasn’t served because it became impure when Sorah touched it, so why did they recite birchas hamazon?
3) Because she violated the commandment not to look back at the destruction of Sodom, Lot’s wife turned into a pillar of salt (19:26). Did she first die and then become a pillar of salt, or did the transformation occur while she was still alive?
4) During selichos we mention: מי שענה לאברהם אבינו בהר המוריה הוא יעננו – “The One who answered Avraham Avinu on Har Hamoria should answer us”. The above is based on the Gemara in Taanis (15b). The question is, which tefillah are we referring to, where do we find Avraham davened on Har Hamoria?
