Musannaf Ibn Abi Shayba 29:144

Ibn ‘Ulayyah narrated to us, from Sa‘id, from Qatadah, from Salim ibn Abi al-Ja‘d, from Ma‘dan ibn Abi Talhah al-Ya‘mari, who said: ‘Umar was struck on Wednesday, with four days remaining of Dhu al-Hijjah.