Hasan al-Basri: Letter to Caliph Umar the Second

I came across this yesterday while studying and wanted to post it here, but didn't have enough time to copy it out of the book. I'm glad I paid attention to it, because it was one of the questions on yesterday's exam.
This letter serves as a good piece of advice for all of us. It's a bit long, so click on the Expand [+] link at the bottom of this post to read the letter.

Beware of this world with all wariness; for it is like to a snake, smooth to the touch, but its venom is deadly. Turn away from whatsoever delights thee in it, for the little companioning though wilt have of it; put off from thee its cares, for that thou hast seen its sudden chances, and knowest for sure that thou shalt be parted from it; endure firmly its hardships, for the ease that shall presently be thine. The more it pleases thee, the more do be wary of it; for the man of this world, whenever he feels secure in any pleasure therof, the world drives him over into some unpleasentness, and whenever he attains any part of it and squats down upon it, the world suddenly turns him upside down. And again, beware of this world, for its hopes are lies, its expectations false; its easefulness is all harshness, muddied its limpidity. And therein thou art in peril: or bliss transient, or sudden calamity, or painful affliction, or doom decisive. Hard is the life of a man if he be prudent, dangerous if comfortable, being wary ever of catastrophe, certain of his ultimate fate. Even had the Almighty not pronounced upon the world at all, nor coined for it any similitude, nor charged men to abstain from it, yet would the world itself have awakened the slumberer, and roused the heedless; how much the more then, seeing that God has Himself sent us a warning against it, an exhortation regarding it! For this world has neither worth nor weight with God; so slight it is, it weighs not with God so much as a pebble or a single clod of earth; as I am told, God has created nothing more hateful to Him than this world, and from the day He created it He has not looked upon it, so much He hates it. It was offered to our Prophet with all its keys and treasures, and that would not have lessened him in God's sight by so much as the wing of a gnat, but he refused to accept it; and nothing prevented him from accepting it-for there is naught that can lessen him in God's sight-but that he knew that God hated a thing, and therefore he hated it, and God despised a thing, and he abased it. Had he accepted it, his acceptance would have been a proof that he loved it; but he disdaned to love what his Creator hated, and to exalt what his Sovereign had debased. As for Muhammad, he bound a stone upon his belly when he was hungry; and as for Moses, the skin of his belly shewed green as grass because of it all: he asked naught of God, the day he took refuge in the shade, save food to eat when he was hungered, and it is said of him in the stories that God revealed to him, "Moses, when thou seest poverty approaching, say, Welcome to the badge of the righteous! and when thou seest wealth approaching, say, Lo! a sin whose punishment has been put on aforetime." If thou shouldst wish, though might name as a third the Lord of the Spirit and the Word (Jesus), for in his affair there is a marvel; he used to say, "My daily bread is hunger, my badge is fear, my raiment is wool, my mount is my foot, my lantern at night is the moon, my fire by day is the sun, and my fruit and fragrant herbs are such things as the earth brings forth for the wild beasts and cattle. All the night I have nothing, yet there is none richer than I!" And if thou shouldst wish, thou mightest name as a fourth David, who was no less wonderful than these; he ate barley bread in his chamber, and fed his family upon bran meal, but his people on fine corn; and when it was night he clad himself in sackcloth, and chained his hand to his neck, and wept until the dawn; eating coarse food, and wearing robes of hair. All these hated what God hates, and despised what God despises; then the righteous thereafter followed in their path and close upon their tracks.