It is narrated from Sayyiduna Sabrah (may Allah be pleased with him) that the Companions saw a cloud and said: O Messenger of Allah, we were hoping that this cloud would rain upon us. He (peace and blessings be upon him) said: "It has been commanded to rain upon the valley of Balil" - meaning a valley called Balil.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 6526