Sahih Bukhari
Asking Permission
Volume: 008 / Book Number: 074 / Hadith Number: 287
Narrated Ibn 'Umar:
The Prophet forbade that a man should be made to get up from his seat so that another might sit on it, but one should make room and spread out. Ibn 'Umar disliked that a man should get up from his seat and then somebody else sit at his place.