بِاسْمِكَ اَللَّهُمَّ أَمُوْتُ وَأَحْيَا

Bismika Allaahumma 'amootu wa 'ahyaa

In Your name O Allah, I live and die. Hudhayfah (RA) said, "If the Messenger of Allah (ﷺ) intended to sleep, he would recite this dhikr.”

Reference: Al-Bukhari, Fathul Bari 11/113 no. 6324, Muslim 4/2083 no. 2711