Musnad Abu Ya'la al-Mawsili 209:58

Narrated to us 'Abd al-Wahid ibn Ghiyath, narrated to us Abu 'Awanah, from Qatadah, from Safinah, the freed slave of Umm Salamah, from Umm Salamah, who said: The general part of the final instruction of the Messenger of Allah (may Allah bless him and grant him peace) during his illness was: "The prayer, and what your right hands possess." He continued to repeat it in his chest, while his tongue could not articulate it clearly.