The Prophet ﷺ said, "A man should not make another man get up from his seat in order to sit in it himself. Rather, make room and spread out for one another."Wazad in another narration, He disliked that a man should rise from his seat and then someone else sit in his place.
عن النبي ﷺ قال: لا يقيم الرجل الرجل من مقعده، ثم يجلس فيه، ولكن تفسحوا وتوسعوا. وزاد في رواية: وكان يكره أن يقوم الرجل من مجلسه، ثم يجلس مكانه.
Bukhari narrated it in the Book of Seeking Permission (6270), and Muslim in the Book of Greetings (2177:28), both through routes from Ubaydullah, from Nafi, from Ibn Umar, who related it. The wording given is Bukhari's, and the additional wording is also Bukhari's. Muslim also narrated it (2177:29) through a route from Zuhri, from Salim, from Ibn Umar, who related it. This version does not contain the phrase, "but make room and open up space for one another," and it adds that when a man would rise from his seat for Ibn Umar, Ibn Umar would not sit in it.I say, this was out of humility on his part. Otherwise, the hadith does not prohibit someone from sitting in a man's place if the man rises of his own accord.