Does this still hold true to Christians today? Yes, of course it does, for it is still God's will that his people -- his children! -- be happy for ever -- and to live! "The glory of God is man fully alive!" So wrote St. Irenaeus. Fully alive with the Holy Spirit in Jesus Christ.
Jesus did not come to abolish the law but to fulfill it. And he has, and so the decrees and laws and customs continue today, but in light of the New Covenant in Jesus, everything is made new, made greater. The two greatest commandments sum up the Law and the Prophets. The sacraments are holy customs to keep, not as mere customs anymore but as signs that actually convey grace, too. And we have the Church, a family structure that is also a kingdom, a royal priesthood, where everyone is already priest, prophet and king, but still on the way to perfection. With the authority of Christ, through his apostles and their successor bishops, Church dogma and laws are still ordered towards the same end: so that we may be happy for ever and live. And so we believe as the Nicene creed sums up. We worship in the celebration of the Eucharist. We are edified in prayer and by Scripture and Tradition. We begin, are nourished and healed along our journey, and end our race by God's grace in the sacraments. We live in harmony and order with our fellows through the decrees of the Church. We glorify God in all ways through the rich diversity of customs, art and all expressions of our faith in Him.
What of this warning by Moses: "Do not follow other gods, gods of the peoples round you, for the Lord your God who dwells among you (!) is a jealous God; his anger could blaze out against you and wipe you from the face of the earth. Do not put the Lord your God to the test as you tested him at Massah." In light of the New Covenant, we know that God's displeasure need not blaze out as it did in the Old Testament. It is terrible enough when we cut ourselves off from him (not the other way around), and so reject his love and his grace, and thus sever our union with him. Jesus is, for us, the mercy of God, the love and compassion of God, the reconciliation with the Father, expressed today not with sacrifices at the temple but through his sacrament of Reconciliation. So there is no excuse even for those who have fallen away: "a humbled, contrite heart you will not spurn" indeed because God is love and mercy.
Truly, The Law of the Lord is perfect: it revives the soul. The rule of the Lord is to be trusted, it gives wisdom to the simple. The command of the Lord is clear, it gives light to the eyes. He who loves his neighbor has satisfied every claim of the l aw: the whole law is summed up in love." (From the responsory in today's Office of Readings.)