Why Should We Take Our Marching Orders from Moses?

And be ye kind one to another, tenderhearted, forgiving one another, even as God for Christ's sake hath forgiven you. - Eph.4:32

    If Decalogue is a perfect and perpetual embodiment of the fulness of our (Christian) duty towards God and neighbor, then which of the ten commandments of the law of Moses specifically teaches us to "forgive one another, even as God for Christ's sake hath forgiven you?"

    This is a rhetorical question. There is NO commandment under the law of Moses which teaches us to forgive one another, even as God for Christ's sake hath forgiven you, for the simple reason that this forgiveness for the sake of Christ is an integral part of the NEW COVENANT, not the old one.

    Why should the NT Christians be taking their marching orders from Moses, if we have a Greater Lawgiver than Moses?