Suhayl bin Abi Salih (may Allah have mercy on him) says: I was with my father when a companion of his peeped into the house of some people and saw a woman; and he mentioned the incident. Then he said: Abu Hurayrah (may Allah be pleased with him) informed us that the Prophet (peace and blessings be upon him) said: "Whoever peeps into the house of a people without their permission and they put out his eye, his eye is of no account."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأشربة والحد فيها / 17657