Musnad Ahmad 17:6

Yazid narrated to us, Sharik ibn Abdullah informed us, from Abu Ishaq, from Burayd ibn Abi Maryam, from Abu al-Hawra’, from al-Husayn ibn Ali, who said: My grandfather—or he said: The Prophet, may Allah bless him and grant him peace—taught me words to say during the Witr prayer. Then he mentioned the hadith.