It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) used to say: "A people receive a blessing by night, then they enter the morning with most of them denying it, saying: 'We have been given rain because of such-and-such naw' (star).'"
Sa'id said: We heard this from Sayyiduna Abu Hurayrah (may Allah be pleased with him). And he narrated to me a hadith from one whom I cannot accuse (of lying): that he was present at the prayer for rain of Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) when he was seeking rain for the people in a year of drought. Sayyiduna Umar (may Allah be pleased with him) and the people supplicated and implored for rain for a long time, and he said to Sayyiduna Abbas bin Abd al-Muttalib (may Allah be pleased with him): O Abbas! How much of the naw' of "al-Thurayya" remains? He said: O Commander of the Believers! The people of knowledge think that after seven days it will move away from the edges of the horizon. The narrator said: By Allah! Those seven days had not yet passed before the people were given rain.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الاستسقاء / 6455