בֵּ֣ית הַ֭לֵּוִי בָּרֲכ֣וּ אֶת־יְהוָ֑ה יִֽרְאֵ֥י יְ֝הוָ֗ה בָּרֲכ֥וּ אֶת־יְהוָֽה׃
O house of Levi, bless ye the LORD; Ye that fear the LORD, bless ye the LORD.
Read kabbalistic (mystical) interpretation of Psalms 135:20: and classical mystical sources.