Musnad Abu Ya'la al-Mawsili 252:37

Abu Bakr ibn Abi Shaybah narrated to us, Zayd ibn al-Hubab narrated to us, from Ayyash al-Hadrami, who said: Yahya ibn Maymun, the judge of Egypt, informed me, saying: Sahl ibn Sa’d narrated to me that the Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever waits for the prayer, he is in a state of prayer as long as he does not commit a hadath (break his ablution)."