from: Hamlet, by William Shakespeare

commonly: "Alas, poor Yorick, I knew him well."

actually: "Alas poor Yorick! I knew him, Horatio"

source: The Complete Works of William Shakespeare

from: The Bible

commonly: "Spare the rod, spoil the child."

actually: "He who spares the rod hates his son, but he who loves him is careful to discipline him."

source: Proverbs 13:24 from The Bible Gateway

from: The Bible

commonly: "Money is the root of all evil."

actually: "For the love of money is the root of all evil" (King James Version), or "For the love of money is a root of all kinds of evil." (New International Version)

source: 1 Timothy 6:10 from The Bible Gateway

from: Casablanca

commonly: "Play it again, Sam"

actually: "Play it"

source: Audio Clip from Casablanca Sound Clips

from: The Divine Comedy, by Dante

commonly: "Abandon hope, all ye who enter here."

actually: "Abandon all hope, you who enter."

source: Reader's Digest Book of Facts. As Alan Krueger, krueger@cs.umn.edu points out, The Divine Comedy was written in Italian. Apart from the object modified by "all", the discrepancy could be attributed to different, equally acceptable, translations.

from: Rime of the Ancient Mariner, (1798) by Samuel Taylor Coleridge

commonly: "Water, water everywhere, and not a drop to drink"

actually: "Water, water everywhere, nor any drop to drink"

source: Rime of the Ancient Mariner, from the collection of S. T. Coleridge works at The University of Virginia Library

from: [Title?], [Date?] by William Congreave

commonly: "Hell hath no fury like a woman scorned."

actually: "Heaven has no rage like love to hatred turned, Nor hell a fury like a woman scorned."

source: CyberNation