"... wehu aharayw (verse 10): “but [she] was behind him.” There are several possible readings of this phrase. If wehuwehi, with the possible meanings that a) “and she [Sarah] was behind him [Yahweh],” or less likely, b) “and it [the door] was behind him [Yahweh].” (The other grammatically possible options are not logically possible, i.e., that “she was behind it [the tent],” or that “it [the door] was behind it [the tent].”) The LXX has ουσα οπισθεν αυτου, “being behind him.” The feminine participle ουσα is nominative, and thus can only refer to Sarah, and not the door or the tent. To judge between these alternatives, we can rule out the interpretation that the phrase would describe Yahweh as behind the tent (MT option b), since the rest of the passage appears to portray the action as occurring in front of the tent. It also seems unlikely that it would describe the door in particular as being behind Yahweh (Samaritan Pentateuch option b), although this is possible. More likely, the meaning is either that the tent was behind Yahweh (Masoretic text option a), or that Sarah was behind Yahweh (Samaritan Pentateuch option a, LXX). The last of these options is the strongest possibility logically, since the point is that Yahweh’s knowledge of Sarah’s laughter is extraordinary ..."