I just read in TCRS Vol. II, pg. 64 in the context of whether or not a person can rightfully deny themselves the Lord's Supper in a degenerative Church (A'Brakel means here a Protestant church and he thinks you cannot and that regardless of the state of the Church you should still take the sacraments), A'Brakel makes mention of the "Covenant of the Old Testament" and says this:
"The Covenant of the Old Testament was not an external covenant, but was none other than the covenant of grace, having the promise of both this present and future life, that is, of both spiritual and temporal benefits, such as in the present case [here referring back to the NT Sacraments]. If one wishes to refer to [the Old Testament] as a National Covenant/I], one is merely saying that the covenant of grace was established with that nation. That it is called a typical covenant is in consequence of it typifying the entire ministry of the coming Messiah."