From when are the three years counted?
Radak: It is from when the rain stopped.
Why did Hashem want to give rain now?
Radak: Due to the famine, many had repented and improved their ways. Also, there were 7,000 in Yisrael who had not bowed to the Ba'al.
Malbim (from Sanhedrin 113a): In order to get the key of Techiyas ha'Mesim, Eliyahu had to return the key of rain to Hashem.
Malbim: Until now, Eliyahu had stopped influence from Above, and could not bring [rain, which gives] life. Now he reversed and brought influence of life to revive the child, so he could bring also rain.
Why must Eliyahu see Achav in order that rain will come?
Malbim: After the rivers dried, [water vapor did not ascend from the ground, so] rain would not come naturally, only via Hashgachah. This will come only with Teshuvah from idolatry 1 .
Hashem's words imply that rain will come in any case! Perhaps He said so because He knew that they will repent. (PF)
Eliyahu swore that also dew will be withheld (17:1). Why should he promise to return only rain?
Ta'anis 3a-b: Dew was not totally withheld, only dew of Brachah. Eliyahu did not mention that he will return also dew, for Achav could claim that it was never withheld (Rashi 3b)!
