Sforno on Genesis
וישתחו לעם הארץ לבני חת. He bowed to the notables present, seeing they represented the whole population.
Or HaChaim on Genesis
ויקם…וישתחו… He arose and bowed down. Abraham explained to them that the reality was the exact opposite of what the Hittites thought. He did not consider himself as a prince amongst them; on the contrary, he considered them as deserving more honour than himself.
Radak on Genesis
ויקם אברהם וישתחו, he rose on his legs and folded them in a manner signifying gratitude for the positive response he had received from the בני חת, informing them next of precisely what it was that he was requesting.