Musannaf Ibn Abi Shayba 3:3910

Abu Bakr narrated to us, he said: 'Abdah bin Sulayman narrated to us, from Isma'il, from Hammad, from Ibrahim, from al-Aswad, from 'Umar, who said: "When it is a cloudy day, then hasten the 'Asr (prayer) and delay the Dhuhr (prayer)."