Musnad Ahmad 1013:17

Abu Abd al-Rahman narrated to us, Ayyash—meaning Ibn Uqbah—narrated to us, Yahya ibn Maymun and Abu al-Husayn Zayd ibn al-Hubab narrated to me. He said: And Ayyash—meaning Ibn Uqbah—narrated to me, he said: Yahya ibn Maymun narrated to me the meaning, Sahl ibn Sa’d stood before us and said: Sahl, I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: "Whoever sits in the mosque waiting for the prayer, he is in a state of prayer."