Aesop - The Shepherd and the Wolf

A Shepherd once found a young Wolf, and brought it up, and after a while taught it to steal lambs from the neighboring flocks. The Wolf, having shown himself an apt pupil, said to the Shepherd: "Since you have taught me to steal, you must keep a sharp look-out, or you will lose some of
your own flock"

The vices we teach may be practiced against us