To see the right and not do it is cowardice.

[見義不爲、無勇也。]

Confucius (c. 551- c. 479 BC) Chinese philosopher, sage, politician [孔夫子 (Kǒng Fūzǐ, K'ung Fu-tzu, K'ung Fu Tse), 孔子 (Kǒngzǐ, Chungni), 孔丘 (Kǒng Qiū, K'ung Ch'iu)]

The Analects [論語, 论语, Lúnyǔ], Book 2, verse 24 (2.24.2) (6th C. BC – AD 3rd C.) [tr. Soothill (1910)]
    (Source)

(Source (Chinese)). Alternate translations:

To see what is right and not to do it is want of courage.
[tr. Legge (1861)]

It is (moral) cowardice to leave undone what one perceives to be right to do.
[tr. Jennings (1895)]

To see what is right and to act against one's judgment shows a want of courage.
[tr. Ku Hung-Ming (1898)]

To see justice and not act upon it is cowardice.
[tr. Pound (1933)]

To see what is right and not do it is cowardice.
[tr. Waley (1938)]

It is cowardice to fail to do what is right.
[tr. Ware (1950)]

Faced with what is right, to leave it undone shows a lack of courage.
[tr. Lau (1979)]

To see what is right and not to do it is cowardice.
[tr. Dawson (1993)]

To not act when justice commands, that is cowardice.
[tr. Leys (1997)]

To see something you ought to do and not to do it is want of courage.
[tr. Huang (1997)]

To see something you ought to do and not to do it is want of courage.
[tr. Huang (1997)]

One does not do the righteous things when one sees them, it is not brave.
[tr. Cai/Yu (1998), #40]

Failing to act on what is seen as appropriate [yi] is a want of courage.
[tr. Ames/Rosemont (1998)]

If he sees what is right but does not do it, he lacks courage.
[tr. Brooks/Brooks (1998)]

And to recognize a Duty without carrying it out is mere cowardice.
[tr. Hinton (1998)]

To see what is right, but to fail to do it, is to be lacking in courage.
[tr. Slingerland (2003)]

To see what is right and not do it is cowardly.
[tr. Watson (2007)]

Faced with what is right yet doing nothing about it shows a lack of courage.
[tr. Chin (2014)]

Being aloof from a righteous obligation is cowardice.
[tr. Li (2020)]