Umar bin Sa'd bin 'Ubaid عمر بن سعد بن عبيد أبو داود · General Behavior (Kitab Al-Adab)

The Messenger of Allah (ﷺ) came upon me when I was sitting thus: having my left hand behind my back and leaning on the fleshy part of it, and said: Are you sitting in the manner of those with whom Allah is angry?

The Prophet (ﷺ) said: When one has a look into the house, then there is no (need of) permission.