He puts his sickle into another man’s harvest.
More French Proverbs:
To go as fast as a friar that is invited to dinner.French
If it rains on the pastor it drops on the vicar.
French
He is a thief indeed who robs a thief.
French
The will is taken for the deed.
French
For some of us happiness comes while we sleep.
French
Nothing is more contagious than a bad example.
French