Faced with what is right, to leave it undone shows a lack of courage.

To see what is right and not to do it is want of courage, or of principle.

Leave undone whatever you hesitate to do

Oh Lord, may I be directed what to do and what to leave undone

If you have got a jacket with a belt, you do not want to leave the belt undone, because it flops around and is distracting.

To see what is right and not to do it, is want of courage. -Confucius Analects.