Musnad Ahmad 32:1701

'Affan narrated to us, Hammad narrated to us, Qatadah, Thabit, and Humayd informed us, from Anas, that a man came and entered the row, and he was out of breath, so he said: "Praise be to Allah, a praise that is abundant, good, and blessed therein." When the Messenger of Allah (peace and blessings of Allah be upon him) finished his prayer, he said: "Which of you spoke the words?" The people remained silent. He said: "Which of you spoke them? For he did not say anything but good." The man said: "I came and I was out of breath, so I said them." He said: "I saw twelve angels rushing to see which of them would raise it." Humayd added, from Anas, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "When one of you comes, let him walk in the manner he was walking, and let him pray what he catches, and complete what he missed." Abu 'Abd al-Rahman said: "Al-irmam means silence."