It is reported that ‘Alî b. Abî Tâlib wrote to Salmâm Al-Farsî – Allâh be pleased with them both – saying:

The likeness of this worldly life (dunyâ) is that of a snake: soft to the touch, it will kill you with its poison. So turn away from what impresses you of it, since what stays with you is so little. And do not be concerned about it, since you are certain about its parting. And be most happy in it when you are most heedful of it; for every time its companion takes solace in one of its delights, it gives way to one of its woes.

Ibn Abî Al-Dunyâ, Kitâb Al-Zuhd article 164.