וְגַם־בַּדֶּ֛רֶךְ כשהסכל [כְּשֶׁסָּכָ֥ל] הֹלֵ֖ךְ לִבּ֣וֹ חָסֵ֑ר וְאָמַ֥ר לַכֹּ֖ל סָכָ֥ל הֽוּא׃
Yea also, when a fool walketh by the way, his understanding faileth him, and he saith to every one that he is a fool.
Read kabbalistic (mystical) interpretation of Ecclesiastes 10:3: and classical mystical sources.