To work in vain; to waste one's effort without achieving any results.

to work hard while accomplishing little; to toil to no avail; to expend effort for no results

An idiom meaning one should not accept a reward or gift without having done something to deserve it; don't get a reward if it is not earned.

(idiom) to receive rewards or payment without having done anything to earn them; literally to receive a salary without having any merit

(idiom) to return without having achieved anything; to come back from a mission or task unsuccessful