A man does not sin by commission only, but often by omission.

[Ἀδικεῖ πολλάκις ὁ μὴ ποιῶν τι, οὐ μόνον ὁ ποιῶν τι.]

Marcus Aurelius (AD 121-180) Roman emperor (161-180), Stoic philosopher

Meditations [To Himself; Τὰ εἰς ἑαυτόν], Book 9, ch. 5 (9.5) (AD 161-180) [tr. Staniforth (1964)]
    (Source)

(Source (Greek)). Alternate translations:

Not he only that committeth, but he also that omitteth something, is oftentimes unjust.
[tr. Casaubon (1634), 9.4]

Omissions no less than Commissions, are oftentimes Branches of Injustice.
[tr. Collier (1701)]

Men are often unjust by omissions, as well as by actions.
[tr. Hutcheson/Moor (1742)]

A man is as often guilty of injustice by omitting to do what he ought, as by doing what he ought not to do.
[tr. Graves (1792), 9.4]

He often acts unjustly who does not do a certain thing; not only he who does a certain thing.
[tr. Long (1862)]

Omissions no less than commission are oftentimes part of injustice.
[tr. Collier/Zimmern (1887)]

Wrong comes often of not doing as well as doing.
[tr. Rendall (1898)]

Men are often unjust by omissions as well as by actions.
[tr. Hutcheson/Chrystal (1902)]

There is often an injustice of omission as well as of commission.
[tr. Haines (Loeb) (1916)]

Often he who omits an act does injustice, not only he who commits an act.
[tr. Farquharson (1944)]

A person often acts unjustly by what he fails to do, and not only by what he does.
[tr. Hard (1997 ed., 2011 ed.)]

And you can also commit injustice by doing nothing.
[tr. Hays (2003)]

There can often be wrongs of omission as well as commission.
[tr. Hammond (2006)]

Very often an unjust act is done by not doing something, not only by doing something.
[tr. Needleman/Piazza (2008)]

One may often injure by omission, not only by action.
[ed. Taplin (2016)]