Why does the Torah see fit to mention that Avraham got up from the presence of his deceased to speak to the Bnei Cheis?
Seforno: Since Sarah was not yet buried, he was not an Aveil, and was therefore permitted to go and speak to the Bnei Cheis.
Rabeinu Bachye: We learn from Avraham that when a person speaks to a public he should stand up. 1
Hadar Zekenim: He wanted to position himself so he could bow to all of them at once.
The Torah records again (in Pasuk 7) that he stood up before speaking to the Bnei Cheis.