Albert Barnes Commentary 1 Kings 1:31

"Then Bath-sheba bowed with her face to the earth, and did obeisance to the king, and said, Let my lord king David live for ever." — 1 Kings 1:31 (ASV)

This was a lower and humbler act of obeisance than before (1 Kings 1:16). In Assyrian sculptures, ambassadors are represented with their faces actually touching the earth before the feet of the monarch.