Reference for Psalms 118:4

יֹֽאמְרוּ־נָ֭א יִרְאֵ֣י יְהוָ֑ה כִּ֖י לְעוֹלָ֣ם חַסְדּֽוֹ׃

So let them now that fear the LORD say, For His mercy endureth for ever.

ספר השרשים