Mishkat al-Masabih #807

Mu'adh b. ‘Abdallah. al-Juhani said that a man of Juhaina told him he had heard God’s Messenger reciting "When the earth is shaken”(Al-Qur’an; 99) in both rak'as of the morning prayer, but did not know whether he had forgotten, or whether he recited it on purpose. Abu Dawud transmitted it.