The Prince by Niccolo Machiavelli Chapter 19 Page 14

account of good actions as of bad; or which reason, as I have already said, a Prince who would maintain his authority is often compelled to be other than good. For when the class, be it the people, the soldiers, or the nobles, on whom you judge it necessary to rely for your support, is corrupt, you must needs adapt yourself to its humours, and satisfy these, in which case virtuous conduct will only prejudice you.

Let us now come to Alexander, who was so just a ruler that among the praises ascribed to him it is recorded, that, during the fourteen years he held the Empire, no man was ever put to death by him without trial. Nevertheless, being accounted effeminate, and thought to be governed by his mother, he fell into contempt, and the army conspiring against him, slew him.