The Law of Moses is a lower law, compared to the Gospels’ higher law, but the higher law’s highest principles are in the lower law, as well.
Jesus identified the two greatest commandments (Matthew 22:35-40; see also D&C 59:5-6), quoting the Old Testament: “Thou shalt love the Lord thy God with all thine heart, and with all thy soul, and with all thy might” (Deuteronomy 6:5). “Thou shalt love thy neighbour as thyself” (Leviticus 19:18).
Other Mosaic verses add helpful insight.
Besides loving our neighbors, we are to treat strangers and outsiders as our own. In Exodus we read, “Thou shalt neither vex a stranger, nor oppress him” – and, as if to show us that he doesn’t just mean fellow believers from out of town, the Lord continues, “for ye were strangers in the land of Egypt” (22:21). Leviticus adds, “The stranger that dwelleth with you shall be as one born among you, and thou shalt love him as thyself; for ye were strangers in the land of Egypt” (19:33-34).
These ancient commandments would surely serve us well in the 21st Century.