כִּ֤י לֹ֣א יִֽ֭שְׁנוּ אִם־לֹ֣א יָרֵ֑עוּ וְֽנִגְזְלָ֥ה שְׁ֝נָתָ֗ם אִם־לֹ֥א יכשולו [יַכְשִֽׁילוּ׃]
For they sleep not, except they have done evil; And their sleep is taken away, unless they cause some to fall.
Read kabbalistic (mystical) interpretation of Proverbs 4:16: and classical mystical sources.