Hadith # 1458
Hudhaifah and Abu Dharr (May Allah be pleased with him) reported: The Messenger of Allah (PBUH) used to supplicate when he went to bed at night: "Bismik-Allahumma ahya wa amut (With Your Name, O Allah, I expire and return to life)."
Every person sleeps at night and gets up in the morning. Thus, in a way, sleep is death and reawakening is gaining life again. This life and death, like the literal life and death, lie in the Hands of Allah. The prayer cited in this Hadith engraves this concept in mind and when one recalls it every night it remains alive in his mind that "this life is for Allah and I am alive with His Will. Whenever He wills, the light of my life will be extinguished. Therefore, I should spend these few days of life lent to me by Him in accordance with His Will and not in His disobedience".