Praise be to Allah.
1. We have not come across any hadith which says that whoever makes someone get up from his seat will be deprived of his seat in Paradise
We have not come across a hadith that says this, that if someone does that, he will be deprived of his seat in Paradise!
2. The ruling on making someone get up from his seat
The one who reaches a permissible place first has more right to it, and it is not permissible for someone else to make him get up from his seat so that he can sit there instead.
It was narrated from Ibn ‘Umar, from the Prophet (blessings and peace of Allah be upon him), that he forbade making a man get up from his seat so that someone else can sit there; rather he told them to accommodate one another and make room.
Narrated by al-Bukhaari (6270) and Muslim 2177).
The Sunnah states that a person has the right to remain in the place where he is sitting until he no longer needs it.
It was narrated from Abu Hurayrah that the Messenger of Allah (blessings and peace of Allah be upon him) said: “If one of you gets up from his seat, then comes back to it, he has more right to it.” Narrated by Muslim (2179).
Al-Qurtubi (may Allah have mercy on him) said:
The Prophet (blessings and peace of Allah be upon him) only forbade making a man get up from where he is sitting because, if someone reaches a seat first, it is his, until he gets up voluntarily, after having fulfilled the purpose for which he was sitting there. It is as if he takes possession of the usage of that place, so it is not permissible for anyone to come between him and what he owns [temporarily].
Based on that, this prohibition may be understood in accordance with the apparent meaning, which is that it is haraam. It was also said that it is to be understood as meaning that it is makrooh (disliked), but the former is more likely to be correct.
End quote from al-Mufhim (5/509).
Ibn Abi Jamrah (may Allah have mercy on him) said:
This applies specifically to places that it is permissible for people to enter and sit in them, either for all people in general, such as mosques, courts and circles of knowledge…
Or it may apply in private spaces, such as when a man invites specific people to his house for a wedding feast or other occasions that are permitted according to Islamic teachings. In these gatherings, whoever sits in a place should not be made to move so that someone else may sit there.
With regard to everything that is permissible, people are all equal, both those of high standing and those of lowly standing. So whoever reaches something first is entitled to it, and the one who is entitled to something on the basis of Islamic teachings, if anything of it is taken away in an unlawful manner that is contrary to Islamic teachings, it has been usurped, and usurping is haraam according to scholarly consensus…
End quote from Nahjat an-Nufoos (4/194).
Shaykh Ibn ‘Uthaymeen (may Allah have mercy on him) said:
The Prophet (blessings and peace of Allah be upon him) forbade that because it is a transgression against one’s brother.
One of the things that we learn from this hadith is that it is haraam to make a man get up from his seat so that one may sit in it. The reason for that is that in principle, saying that one should not do something means that it is prohibited (haraam). The fact that it is prohibited is supported by the fact that it is a transgression against another person, and the basic principle regarding transgression against others is that it is haraam.
Another thing that we learn from this hadith is that a man has more right to his seat so long as his need for it has not come to an end, so he should not be asked to leave it. That includes his place in the mosque, his place in the study circle, his place in a marketplace, his place in any location. He has more right to it so long as he has not left it…
End quote from Sharh Buloogh al-Maraam (6/252-253).
Conclusion: Whoever makes someone get up from a permissible place that he reached first is wronging him, and he should ask him to forgive him and not expose himself to retaliation on the Day of Resurrection when the issue will be settled with hasanaat (good deeds) and sayyi’aat (bad deeds).
It was narrated from Abu Hurayrah that the Messenger of Allah (blessings and peace of Allah be upon him) said: “Whoever has wronged his brother, let him seek his forgiveness, for there [in the hereafter] there will be no dinar and no dirham, and before some of his hasanaat (good deeds) will be taken and given to his brother and if he has no hasanaat to his credit, then some of his brother’s sayyi’aat (bad deeds) will be taken and thrown onto him.
Narrated by al-Bukhaari (6534).
And Allah knows best.