Tosefta for Psalms 136:19

לְ֭סִיחוֹן מֶ֣לֶךְ הָאֱמֹרִ֑י כִּ֖י לְעוֹלָ֣ם חַסְדּֽוֹ׃

Sihon king of the Amorites, For His mercy endureth for ever;