Sayyiduna Sahl bin Sa'd (may Allah be pleased with him) says: Once the Prophet (peace and blessings be upon him) was in his apartment, and he (peace and blessings be upon him) had a comb with which he (peace and blessings be upon him) was combing his beard, when a man came and began peeping through a hole in his (peace and blessings be upon him) apartment. The Prophet (peace and blessings be upon him) saw him and said: "Had I known that you were waiting for me, I would have thrust this comb into your eye. Seeking permission has only been prescribed because of the sight." (A note on the chain:) This Abu Salamah, from whom Sufyan narrates, is in fact Muhammad bin Abi Hafsah.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5647