בִּנְפֹ֣ל אויביך [אֽ֭וֹיִבְךָ] אַל־תִּשְׂמָ֑ח וּ֝בִכָּשְׁל֗וֹ אַל־יָגֵ֥ל לִבֶּֽךָ׃
Rejoice not when thine enemy falleth, And let not thy heart be glad when he stumbleth;
Read kabbalistic (mystical) interpretation of Proverbs 24:17: and classical mystical sources.