Charles Ellicott Commentary Deuteronomy 6:25

"And it shall be righteousness unto us, if we observe to do all this commandment before Jehovah our God, as he hath commanded us." — Deuteronomy 6:25 (ASV)

And it shall be our righteousness. —In one Targum, “It shall be merit to us,” or more fully, in the other, “It shall be merit laid up for us against the world to come.” In the Septuagint, “It shall be alms to us.” This conjunction of ideas will help to explain why in Matthew 6:1 “alms” and “righteousness” occur as alternative readings. We have “alms” in the Authorised Version, “righteousness” in the Revised Version. To this day the Jews call alms ts’dâkah, “righteousness.”