لَا إِلٰهَ إِلَّا اللّٰهُ إِنَّ لِلْمَوْتِ سَكَرَاتٍ
Aaishah (radhi-yAllaahu anhaa) related that The Prophet (sal-Allaahu alayhe wa sallam) [during his illness in which he passed away] would dip his hands in water and then he would wipe his face and say:
لَا إِلٰهَ إِلَّا اللّٰهُ إِنَّ لِلْمَوْتِ سَكَرَاتٍ
There is none worthy of worship but Allah, surely death has agonies.
Al-Bukhari, cf. Al-Asqalani, Fathul-Bari 8/144. The Hadith also mentions him using the Siwak (tooth stick).