O’ people. Every one has to meet what he wishes to avoid by running away. Death is the place to which life is driving. To run away from it means to catch it. How many days did I spend in searching for the secret of this matter, but Allah did not allow save its concealment. Alas! It is a treasured knowledge. As for my last will, it is that concerning Allah, do not believe in a partner for Him, and concerning Muhammad (p.b.u.h.a.h.p.), do not disregard his Sunnah. Keep these two pillars and burn these two lamps. Till you are not divided, no evil will come to you. Every one of you has to bear his own burden. It has been kept light for the ignorant. Allah is Merciful. Faith is straight. The leader (Prophet) is the holder of knowledge. Yesterday I was with you; today I have become the object of a lesson for you, and tomorrow I shall leave you. Allah may forgive me and you.
If the foot remains firm in this slippery place, well and good. But if the foot slips, this is because we are under the shade of branches, the passing of the winds and the canopy of the clouds whose layers are dispersed in the sky, and whose traces disappeared in the earth. I was your neighbour. My body kept you company for some days and shortly you will find just an empty body of mine which would be stationary after (all its) movement and silent after speech so that my calmness, the closing of my eyes, and the stillness of my limbs may provide you counsel, because it is more of a counsel for those who take a lesson (from it) than eloquent speech and a ready word. I am departing from you like one who is eager to meet (someone). Tomorrow you will look at my days, then my inner side will be disclosed to you and you will understand me after the vacation of my place and its occupation by someone else.
Source: Nahjul Balagha, Sermon no. 148