Musnad Ahmad 1156:185

Bahz narrated to us, Hammam narrated to us, Qatadah narrated to us, from Abu al-Khalil, from Safinah, the freed slave of Umm Salamah, from Umm Salamah, that when the Prophet (peace and blessings of Allah be upon him) was near death, he began to say: "The prayer, the prayer, and what your right hands possess." He kept repeating it, and his tongue could barely articulate it.