(4) The Book of the Etiquette of Sleeping, Lying and Sitting etc
كتاب آداب النوم
(129) Chapter: Etiquette of Attending company and sitting with Companions
(129) - باب في آداب المجلس والجليس
Riyad as-Salihin 824 
Ibn 'Umar (May Allah be pleased with them) reported:
Messenger of Allah (ﷺ) said, "Do not ask someone to give up his seat in order to take it, but make accommodation wide and sit at ease." It was Ibn 'Umar's habit that if a person left his seat for him, he would not take it.


[Al-Bukhari and Muslim].

عن ابن عمر رضى الله عنهما قال‏:‏ قال رسول الله صلى الله عليه وسلم‏:‏ ‏ "‏لا يقمن أحدكم من مجلسه ثم يجلس فيه، ولكن توسعوا وتفسحوا‏"‏ وكان ابن عمر إذا قام له رجل من مجلسه لم يجلس فيه‏.‏ (‏‏(‏متفق عليه‏)‏‏)‏.
Reference : Riyad as-Salihin 824
In-book reference : Book 4, Hadith 12