והבור רק אין בו מים. פירש"י מים אין בו אבל נחשים ועקרבים יש בו. פי' דרק ואין הוי מיעוט אחר מיעוט ואין מא"מ אלא לרבות לומר שהיה בו שום דבר. וא"ת ומנא ליה דנחשים הוי אימא אבנים יש בו. י"ל מדכתיב רק משמע דבר שלפעמים היה מתרוקן ממנו: והבור רק אי בו מים, “the pit was empty, not containing any water.” Rashi comments that this is to tell us that while there was no water in the pit in which he could have drowned, there were other hazardous inhabitants in that pit such as snakes and scorpions. (based on B’reshit Rabbah 84,16.) This interpretation is based on the principle that when two negatives follow one another this indicates that we are being told something positive, even if not beneficial. It would have sufficed to describe the pit as simply: “empty.” If you were to ask why did it have to refer to the presence of scorpions? What hint is there of that? Maybe there were merely stones inside the pit? The expression רק for empty, instead of ריק means that it was empty on occasion but filled with water at other times. Scorpions take refuge there when it has been emptied from water.