It is permissible to stand up
to greet someone joining or passing by a gathering. The Prophet (peace be upon him) said to the Ansar:
Stand up to receive your chieftain,
Sa`d ibn Mu`adh (may Allah be pleased with him) was coming to express his judgment on
Talhah ibn `Ubaydullah (may Allah be pleased with him) stood up for
Ka`b ibn Malik while sitting in the teaching circle of the Prophet (peace be upon him) when
Ka`b came to the Prophet (peace be upon him) to shake hands with him and congratulate him on Allah's accepting his repentance along with his other two Companions.
Furthermore, the Prophet (peace be upon him) would stand up for his daughter Fatimah (Part No. 24; Page No. 130) when she would come to him, take her hands, kiss her and let her take his seat. Likewise, whenever the Prophet (peace be upon him) came to her she would stand up for him, take his hand and kiss him.
As for standing up to merely glorify or show respect and not for greeting, it is impermissible. This is based on the Hadith:
Let he who likes people to stand up before him assume his seat in Hell.
Abu Dawud and
Al-Tirmidhy through a trustworthy Isnad (chain of narrators).May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.