Tosefta for Psalms 136:10

לְמַכֵּ֣ה מִ֭צְרַיִם בִּבְכוֹרֵיהֶ֑ם כִּ֖י לְעוֹלָ֣ם חַסְדּֽוֹ׃

To Him that smote Egypt in their first-born, For His mercy endureth for ever;