Nature has given us friendship as the handmaid of virtue, not as a partner in guilt
 Marcus Tullius Cicero, On Friendship (44 BC). copy citation

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Author Marcus Tullius Cicero
Source On Friendship
Topic friendship guilt
Date 44 BC
Language English
Reference
Note Translated by E. S. Shuckburgh
Weblink http://www.gutenberg.org/files/2808/2808-h/2808-h.htm

Context

“when, that is to say, men who are united by affection learn, first of all, to rule those passions which enslave others, and in the next place to take delight in fair and equitable conduct, to bear each other's burdens, never to ask each other for anything inconsistent with virtue and rectitude, and not only to serve and love but also to respect each other. I say "respect"; for if respect is gone, friendship has lost its brightest jewel. And this shows the mistake of those who imagine that friendship gives a privilege to licentiousness and sin. Nature has given us friendship as the handmaid of virtue, not as a partner in guilt: to the end that virtue, being powerless when isolated to reach the highest objects, might succeed in doing so in union and partnership with another. Those who enjoy in the present, or have enjoyed in the past, or are destined to enjoy in the future such a partnership as this, must be considered to have secured the most excellent and auspicious combination for reaching nature's highest good.” source