Musannaf Ibn Abi Shaybah 7115 — Those who said qunut is in the second

Al-Hasan says that Sayyiduna Ubayy (may Allah be pleased with him) led the people in prayer during the caliphate of Sayyiduna Umar (may Allah be pleased with him). He did not recite the qunut supplication in the prayer until the middle of Ramadan; when the middle of Ramadan had passed, he recited the qunut supplication after bowing (ruku'). When the last ten days began, he went away and withdrew from the people. Then, during the caliphate of Sayyiduna Umar (may Allah be pleased with him), Sayyiduna Mu'adh al-Qari (may Allah be pleased with him) led them in prayer during the last ten days.