What are the connotations of ?Vayakam Avraham me'al-P?nei Meiso"? What is it coming to teach us??
Seforno: Since Sarah was not yet buried, he was [an Onen, and] not an Aveil, and was therefore permitted to go and speak to the Bnei Ches.
Rabeinu Bachye: We learn from Avraham that when a person speaks to the public, he should stand up. 1
Hadar Zekenim: He positioned himself so he could prostrate himself to all of them at once.
Ohr ha'Chayim: This hints that a Mes knows what is said in front of it, until the coffin is sealed (Shabbos 152b), and hints to the custom to bury a Mes lying on its back.
The Torah records again (in 23:7) that he stood up before speaking to the Bnei Ches.
Why does it say "va'Yedaber" and also "Leimor"?
Ohr ha'Chayim: He requested a burial place, which implies any place; and said "Tenu" (32:4) which implies a free gift. Then, he clarified that he wants specifically Efron's field, and that he does not want a gift.
Why does it say "va'Yakom" rather than "va'Ya'amod"?
Ha'amek Davar: It was hard to leave his Mes and the eulogy; nevertheless he got up with zealousness.
