For one must indeed assist one's friend but not do anything wrong for him, one must advise with him but not plot with him, one must bear witness for him but not join him in fraud, one must certainly share adversity with him but not crime. For since we should not wish even to know of our friends' dishonourable acts, much less should we desire to share their dishonour by acting with them.
 Plutarch, Moralia (c. 100 AD). copy citation

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Author Plutarch
Source Moralia
Topic adversity fraud
Date c. 100 AD
Language English
Reference
Note Translated by Arthur Richard Shilleto
Weblink http://www.gutenberg.org/files/23639/23639-h/23639-h.htm

Context

“He will therefore rather try and turn him away from what is not becoming, and if he cannot persuade him, good is that answer of Phocion to Antipater, "You cannot have me both as friend and flatterer,"438 that is, as friend and no friend. For one must indeed assist one's friend but not do anything wrong for him, one must advise with him but not plot with him, one must bear witness for him but not join him in fraud, one must certainly share adversity with him but not crime. For since we should not wish even to know of our friends' dishonourable acts, much less should we desire to share their dishonour by acting with them. As then the Lacedæmonians, when conquered in battle by Antipater, on settling the terms of peace, begged that he would lay upon them what burdens he pleased, provided he enjoined nothing dishonourable, so the friend, if any necessity arise involving expense or danger or trouble, is the first to desire to be applied to and share in it with alacrity and without crying off, but if there be anything disgraceful in connection with it he begs to have nothing to do with it.” source