Regardless if we think we are deserving or undeserving (which is the case), union with God comes with a complete package (2 Pet 1:3), which was completed on the Cross when Christ said “it is finished” (John 19:30).
“Covenant” and “Grace” are not in opposition but in parallel, in that each lies within succession of one another. Grace established union, while Covenant pointed to fellowship within the pre-established union. Once union with God has been established, it cannot vary (Rom 11:29), but the fellowship within the union can and should, towards the “drawing nigh to God” (Jam 4:8), which one can only “enter into the Holiest by the blood of Jesus” (Heb 10:19); “by the which we draw nigh unto God” (Heb 7:19).
Union once established, provides potential for a progression of fellowship by way of, not conforming, but “being conformed” (Rom 8:29; 12:2)—“from glory to glory” (2 Cor 3:18); which fellowship requires time and learning to mature. First, by example of the “schoolmaster”, which was the Law to Israel (Gal 3:24), who were in type, representative for all mankind; then, by the Master of the school—Christ, via His and the Father’s Spirit (John 14:26).
Israel’s union with God was not covenanted, for He established union with them - to be their God and them to be His people - before the Law was given (Gen 17:8; Exd 34:27, 28). The Law Covenant God made with them was not intended to provide for fellowship through adherence to it; but to reveal the way of fellowship; by types and “shadows” (Col 2:7; Heb 8:5; 10:1) which were symbolic representations of Christ, through whom the Father would eventually procure communion within the union.
God prepared the Law with specifications that He knew no man cold keep without ever breaking it to show the only way to Him was, not by anything man could do, but by what His Son did (John 14:6). Since only Christ could keep the Law perfectly, He was the One to complete or “end it” (Rom 10:4). “For if that first covenant had been faultless, then should no place have been sought for the second” so “He taketh away the first, that he may establish the second” (Heb 8:7; 10:9).
“The Law was given for the sake of Christ, for it had not been given had it not been for Him; all its institutions, ordinances, and sacrifices, were on His account: they were all shadows of Him, and He the body and substance of them; He was the end or mark and scope at which they all aimed; every type looked to Him, and every offering directed the worshipper to Him.” - J Gill.
This is why it is written that righteousness is “fulfilled”, not by us, but “in us” (Rom 8:4)—through Christ; “who of God is made unto us . . . righteousness. . . .” (1 Cor 1:30). He does not want our fellowship to be based on the fear of obeying law, for “The purpose of the commandment is love from a pure heart” (1 Tim 1:5), which the Law wasn’t intended to deliver (Rom 8:3).
This is what is meant by the Law was a “schoolmaster”, in that it was preparatory only for the concept and not the application of fellowship. The tutoring of the Law is similar to the ministry of John the Baptist (Mat 3:3), in that they only “prepared” for union with God. Even though He knew there would be times of breaking His covenant, it would not affect Israel’s union with Him, which was evidenced by His continual chastisements in causing them to desire His provisions again.
This was a union without fellowship with God, for “The Holy Ghost this signifying, that the way into the holiest of all was not yet made manifest, while as the first tabernacle was yet standing” (Heb 9:8), which infers that Christ is the second tabernacle; “But Christ being come an high priest of good things to come, by a greater and more perfect tabernacle” (Heb 9:11), who has “not entered into the holy places made with hands, which are the figures of the true; but into heaven itself, now to appear in the presence of God for us” (Heb 9:24; Rev 21:3).
I say the Law was only preparatory and not provisional, because “it was weak through the flesh” [old man or Adamic-nature} – (Rom 8:3). It was only “a shadow of good things to come” (Heb 10:1) which could only teach one to come “unto Christ” (Gal 3:24); then through Him the provision would be established concerning fellowship with “the very image of the things” (Heb 10:1) of God. “For ye are not come unto the mount that might be touched” (Heb 12:18), “But ye are come unto mount Sion” (Heb 12:22; Mic 4:7).