Musnad Ahmad 1017:120

Waki’ narrated to us, al-Awza’i narrated to us, from Yahya ibn Abi Kathir, from Abu Qilabah, from Abu al-Muhajir, from Buraydah, who said: We were with him on a military expedition. He said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: "Hasten to the prayer on a cloudy day, for whoever misses the Asr prayer, his deeds have been rendered void."