Musnad Ahmad 1155:48

Waki’ narrated to us, from Nafi’ ibn ‘Umar, and Abu ‘Amir narrated to us, Nafi’ narrated, from Ibn Abi Mulaykah, from one of the wives of the Prophet, may Allah bless him and grant him peace. Abu ‘Amir said: Nafi’ said: I think it was Hafsah, that she was asked about the recitation of the Messenger of Allah, may Allah bless him and grant him peace, and she said: "You would not be able to do it." It was said to her: "Inform us of it." She recited a recitation in which she slowed down. Abu ‘Amir said: Nafi’ said: Ibn Abi Mulaykah demonstrated for us: "Al-hamdu lillahi rabbil-'alamin" (Praise be to Allah, Lord of the worlds). Then he paused. "Ar-rahmanir-rahim" (The Most Gracious, the Most Merciful). Then he paused. "Maliki yawmid-din" (Master of the Day of Judgment).