Cujus per errorem dati repetitio est
Cujus per errorem dati repetitio est, ejus consulto dati donatio est. Whoever pays by mistake what he does not owe, may recover it back; but he who pays, knowing he owes nothing; is presumed to give.
A Law Dictionary, Adapted to the Constitution and Laws of the United States. By John Bouvier. Published 1856.