The Forty Hadiths of al-Nawawi.
On the authority of Ibn 'Umar (may Allah be pleased with them both), who said:
The Messenger of Allah (peace and blessings of Allah be upon him) took hold of my shoulder and said:
"Be in this world as though you were a stranger or a wayfarer."
And Ibn 'Umar used to say:
"When evening comes, do not anticipate the morning,
and when morning comes, do not anticipate the evening.
Take from your health for your illness,
and from your life for your death."
Related by al-Bukhari.
This hadith explains the true reality of the worldly life:
that it is a temporary transit, not an abode of permanent rest.
Thus, it calls upon the Muslim not to become attached to it
or preoccupied with its transient adornments,
but rather to prepare and strive for the Hereafter.
For the believer lives in it like a stranger,
never taking it as a permanent homeland,
or like a traveler whose sole concern is reaching his final destination.
Therefore, this hadith nurtures asceticism and a curtailing of worldly hopes,
encourages seizing time in acts of obedience,
and warns against heedlessness regarding one's ultimate destiny.