King James Version (KJV)
To him that smote Egypt in their firstborn: for his mercy endureth for ever:
Modern English
to him who struck down the firstborn of Egypt, for his steadfast love endures forever;
Hebrew
לְ֭מַכֵּה מִצְרַ֣יִם בִּבְכוֹרֵיהֶ֑ם כִּ֖י לְעוֹלָ֣ם חַסְדּֽוֹ׃
lmakeh miṣrayim bibkvoreyhem kiy lʿvolam ḥasdvo