Midrash for Deuteronomy 6:25

"He did the righteousness (tzedakah) of the L-rd": What kind of tzedakah did he do with Israel? All the forty years that Israel were in the desert, the well (of Miriam) rose up for them, and the manna descended for them, and the quail abounded for them, and the clouds of glory surrounded them! But (the tzedakah was that) he taught Torah to Israel, viz. (Devarim 6:25) "And it shall be (accounted) tzedakah to us if we observe to do all the words of this Torah."