not hurt a fly

not hurt a fly

not injure or upset anyone or anything She said the arrest was a mistake, that her husband wouldn't hurt a fly.
Usage notes: also used in the forms can't hurt a fly, couldn't hurt a fly, and would never hurt a fly: He was so gentle he would never hurt a fly.
See also: fly, hurt, not

not hurt a fly

Also, not hurt a flea. Not cause harm to anyone, be gentle and mild, as in Paul's the kindest man-he wouldn't hurt a flea, or Bert has a temper but it's all talk; he wouldn't hurt a fly. Both fly and flea are used in the sense of "a small insignificant animal." [Early 1800s]
See also: fly, hurt, not
References in classic literature ?
Shuan would not hurt a fly except when he was drinking.
Oh, believe me, my anger means nothing; I could not hurt a fly," I smiled back bitterly.