It is narrated from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Whoever peeps into the house of a people without their permission, it becomes lawful for them to put out his eye."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الأشربة والحد فيها / 17656