Why does it mention here that he hid Nevi'im in a cave?
Rashi: It explains how he feared Hashem greatly. Radak - he risked his life greatly to sustain Nevi'ei Hashem.
Malbim: This merit would stand for him at a time of hunger, like it says about Nechuniya, who used to dig pits [so water would be available for the Rabim]. Something he toiled for, his seed would not stumble in (perish through) it (Bava Kama 50b)!
Why did he hide only 50 in a cave?
Radak: The other 50 were in another cave. Sanhedrin 39b - some say that he learned from Yakov, who split his camp, lest Esav kill part. And some say that only 50 fit in one cave.
Food was so scarce that the widow and her son would have starved if not for the miracle. How was Ovadyah able to sustain 100 Nevi'im?
Tanchuma (Mishpatim 9): He was wealthy, the overseer of Achav's house, and he borrowed from Yehoram ben Achav, with Ribis 1 , in order to feed the Nevi'im.
Midrash ha'Gadol (Chayei Sarah 23:1): Ovadyah's widow is the one who screamed to Elisha that the creditor (Yehoram) is coming to take her children to be slaves (Melachim II, 4:1). She said, are you not among the Bnei ha'Nevi'im that my husband hid?!
It says that he brought food. Why must it mention supplying also water?
Radak: Water was expensive in the years of hunger. Bereishis Rabah 19:12 - it was harder to bring to them water than to bring food!
