Musnad Ahmad 30:3003

Asbat narrated to us, he said: Al-A’mash narrated to us, from Ibrahim, from Ibn Mas’ud, from the Prophet, may Allah bless him and grant him peace, he said: And Al-A’mash narrated to us, from Abu Salih, from Abu Hurairah, from the Prophet, may Allah bless him and grant him peace, regarding the saying of the Almighty, Exalted is He: {And the recitation of the dawn; indeed, the recitation of the dawn is ever witnessed} [Al-Isra: 78]. He said: "The angels of the night and the angels of the day witness it."