Musnad Ahmad 30:3750

Abdullah ibn al-Harith narrated to us, from al-Dahhak, from Sa’id ibn Abi Sa’id al-Maqburi, from Abu Hurairah, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "The Muslim servant remains in a state of prayer as long as he is sitting in his place of prayer, and nothing detains him except the waiting for the prayer. And the angels say: 'O Allah, forgive him; O Allah, have mercy upon him,' as long as he does not commit a hadath (break his ablution)."