רַ֞ק עֵ֣ץ אֲשֶׁר־תֵּדַ֗ע כִּֽי־לֹא־עֵ֤ץ מַאֲכָל֙ ה֔וּא אֹת֥וֹ תַשְׁחִ֖ית וְכָרָ֑תָּ וּבָנִ֣יתָ מָצ֗וֹר עַל־הָעִיר֙ אֲשֶׁר־הִ֨וא עֹשָׂ֧ה עִמְּךָ֛ מִלְחָמָ֖ה עַ֥ד רִדְתָּֽהּ׃ (פ)
Only the trees of which thou knowest that they are not trees for food, them thou mayest destroy and cut down, that thou mayest build bulwarks against the city that maketh war with thee, until it fall.
Read kabbalistic (mystical) interpretation of Deuteronomy 20:20: and classical mystical sources.