If any layman has desired to commit adultery or fornication with a married woman, and has lusted after his neighbour's wife, and not committed the act, that is, has not been able to, because the woman did not allow him, yet he was ready to fornicate, let him confess his guilt to the priest, and so let him do penance for forty days on bread and water.’’
cf. Paen. Venniani 17