Musannaf Ibn Abi Shayba 3:3968

Hussain bin Ali narrated to us, from Za'idah, from Mis'ar, from Ibrahim, from Abd al-Rahman bin Yazid, that he used to recite in the two rak'ahs before the dawn (prayer) and the two rak'ahs after the sunset (prayer): "Say, 'O disbelievers,'" and "Say, 'He is Allah, [who is] One.'"