כְּעַ֤ל גְּמֻלוֹת֙ כְּעַ֣ל יְשַׁלֵּ֔ם חֵמָ֣ה לְצָרָ֔יו גְּמ֖וּל לְאֹֽיְבָ֑יו לָאִיִּ֖ים גְּמ֥וּל יְשַׁלֵּֽם׃
According to their deeds, accordingly He will repay, Fury to His adversaries, recompense to His enemies; To the islands He will repay recompense.
Read kabbalistic (mystical) interpretation of Isaiah 59:18: and classical mystical sources.