So a man as long as he doth that which is proper unto a man, his labour cannot be against nature
 Marcus Aurelius, Meditations (c. 170 - 180). copy citation

add
Author Marcus Aurelius
Source Meditations
Topic labour
Date c. 170 - 180
Language English
Reference
Note Translated by Meric Casaubon
Weblink https://en.wikisource.org/wiki/Marcus_Aurelius_Antoninus_-_His_Meditatio...

Context

“for as for future and past operations, those also are now at this present indifferent unto her. XXXI. As long as the foot doth that which belongeth unto it to do, and the hand that which belongs unto it, their labour, whatsoever it be, is not unnatural. So a man as long as he doth that which is proper unto a man, his labour cannot be against nature; and if it be not against nature, then neither is it hurtful unto him. But if it were so that happiness did consist in pleasure: how came notorious robbers, impure abominable livers, parricides, and tyrants, in so large a measure to have their part of pleasures?” source