It is narrated from Sayyiduna Ka'b bin Murrah (may Allah be pleased with him) that he narrated to us a hadith that he had heard from the Messenger of Allah (peace and blessings be upon him). He said: I heard the Messenger of Allah (peace and blessings be upon him) when he (peace and blessings be upon him) invoked against the tribe of "Mudar". So I came to him (peace and blessings be upon him) and said: O Messenger of Allah! Indeed Allah Almighty has granted you (what you asked) and has answered your supplication, and indeed your people have perished, so supplicate for them. So he (peace and blessings be upon him) supplicated: 'Allahumma-sqina ghaythan mughithan mari'an mari'an nafi'an ghayra darrin, 'ajilan ghayra ajil' (O Allah, give us beneficial rain that relieves and quenches, that brings lushness, that satisfies and brings abundance, that comes soon and not late, that is beneficial and not harmful). Then not even a Friday, or a time equal to it, had passed before they were given rain.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الاستسقاء / 6440