Musnad Ahmad 30:2262

'Affan and Bahz narrated to us, they said: Abu 'Awanah narrated to us, from Ya'la ibn 'Ata, from Abu 'Alqamah al-Ansari, who said: Abu Hurayrah narrated to me, from his mouth to my mouth, he said: I heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Whoever obeys me has obeyed Allah, and whoever disobeys me has disobeyed Allah. Whoever obeys the commander has obeyed me. The commander is only a shield; if he prays sitting, then pray sitting. And when he says: 'Allah hears those who praise Him' (Sami' Allahu liman hamidah), then say: 'O Allah, our Lord, to You is the praise' (Allahumma Rabbana laka al-hamd). For if the saying of the people of the earth coincides with the saying of the people of the heaven, his past sins will be forgiven."