Musnad Ahmad 1153:468

Mansur ibn Salamah narrated to us, he said: Layth informed us, from Yazid ibn al-Had, from Musa ibn Sarjas, from al-Qasim ibn Muhammad, from Aisha, she said: I saw the Messenger of Allah, may Allah bless him and grant him peace, while he was dying, and beside him was a cup containing water. He was inserting his hand into it, then wiping his face with it, and saying: "O Allah, help me against the agonies of death."