Sahih Bukhari Volume 008, Book 076, Hadith Number 425.

Narated By Mujahid : 'Abdullah bin 'Umar said, "Allah's Apostle took hold of my shoulder and said, 'Be in this world as if you were a stranger or a traveler." The sub-narrator added: Ibn 'Umar used to say, "If you survive till the evening, do not expect to be alive in the morning, and if you survive till the morning, do not expect to be alive in the evening, and take from your health for your sickness, and (take) from your life for your death."