Musnad Ahmad 1015:6

Muhammad ibn Ja‘far narrated to us, Sa‘id narrated to us, from Qatadah, from Shahr ibn Hawshab, from ‘Abd al-Rahman ibn Ghanm, from Abu Malik al-Ash‘ari, that he said to his people: "Gather, so that I may lead you in the prayer of the Messenger of Allah, peace and blessings of Allah be upon him." When they gathered, he said: "Is there anyone among you who is not of you?" They said: "No, except for a son of our sister." He said: "The son of a sister of a people is one of them." Then he called for a bowl containing water. He performed ablution, rinsed his mouth, inhaled water into his nose, washed his face three times, and his forearms three times each. He wiped his head and the tops of his feet. Then he led them in prayer. He recited twenty-two takbirs with them, saying the takbir when he prostrated and when he raised his head from prostration. In the two rak‘ahs, he recited the Opening of the Book (Al-Fatihah) and made those who were next to him hear it.