Asim Ahwal (may Allah have mercy on him) says that I asked Hazrat Anas (may Allah be pleased with him): Is Qunoot before or after Ruku? He replied: Before Ruku. I said: Some people think that the Prophet (peace and blessings be upon him) recited Qunoot after Ruku? He replied: They are mistaken; the Prophet (peace and blessings be upon him) recited it after Ruku only for one month, during which he supplicated against those who martyred his reciter companions.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 12705