Qaasim bin Muhammad Radiyallahu 'Anhu reports that 'Aayeshah Radiyallahu 'Anha said:
"I had seen Rasulullah Sallallahu 'Alayhi Wasallam at the time of his death, a cup of water was near him. He was putting his hands in the cup and wiping his face with it. (At the time of intense heat and unrest it calms one). Then he was reciting: 'O Allah help me in the difficulties of death'"
English reference: Book 53, Hadith 370
Arabic reference: Book 54, Hadith 387