"Judge not, ___ ye be judged" (4)
![Ross](/clue/static/ross-mug.min.png)
I believe the answer is:
lest
(Other definitions for lest that I've seen before include "For fear that; in order to prevent" , "For fear that (something happens)" , "To avoid the risk that - we forget?" , "In order not to, to avoid the risk that" , "To avoid the risk that - let's do it" .)