What are your thoughts on this from Pinks The Divine Covenants: We will now consider the seal which the Lord God made upon the covenant into which He entered with the federal head of our race. This is admittedly the most difficult part of our subject, and for that reason, the least understood in most circles today. So widespread is the spiritual ignorance which now prevails that, in many quarters, to speak of “the seal” of a covenant is to employ an unintelligible term. And yet the seal is an intrinsic part and an essential feature in the various covenants which God made. Hence, our treatment of the Adamic covenant would be quite inadequate and incomplete did we fail to give attention to one of the objects which is given a central place in the brief Genesis record. Mysterious as that object appears, light is cast on it by other passages. Oh, that the Holy Spirit may be pleased to guide us into the truth thereon! “And out of the ground made the Lord God to grow every tree that is pleasant to the sight, and good for food; the tree of life also in the midst of the garden, and the tree of knowledge of good and evil” (Gen. 2:9). First of all, let it be said emphatically that we regard this verse as referring to two real and literal trees: the very fact that we are told they were “pleasant to the sight” obliges us to regard them as tangible and visible entities. In the second place, it is equally obvious from what is said of them that those two trees were extraordinary ones, peculiar to themselves. They were placed “in the midst of the garden”; and from what is recorded in connection with them in Genesis 3, it is clear that they differed radically from all the other trees in Eden. In the third place, we cannot escape the conclusion that those literal trees were vested with a symbolical significance, being designed by God to give instructions to Adam, in the same way as others of His positive institutions now do unto us. “It hath pleased the blessed and almighty God, in every economy of His covenants, to confirm, by some sacred symbols, the certainty of His promises and at the same time to remind man in covenant with Him of his duty” (H. Witsius). Examples of that fact or illustrations of this principle may be seen in the rainbow by which God ratified the covenant into which He entered with Noah (Gen. 9:12, 13), and circumcision which was the outward sign of confirmation of the covenant entered into with Abraham (Gen. 17:9, 11). From these cases, then, we may perceive the propriety of the definition given by A. A. Hodge: “A seal of a covenant is an outward visible sign, appointed by God as a pledge of His faithfulness, and as an earnest of the blessings promised in the covenant.” In other words, the seal of the covenant is an external symbol, ratifying the validity of its terms, as the signatures of two witnesses seal a man’s will. Now as we have shown in previous chapters, the language of Genesis 2:17 not only pronounced a curse upon the disobedient partaking of the fruit of the tree of knowledge of good and evil, but by necessary implication it announced a blessing upon the obedient non-eating thereof. The curse was death, with all that that involved and entailed; the blessing was a continuance and confirmation in all the felicity which man in his pristine innocence enjoyed. In His infinite conde*scension the Lord God was pleased to confirm or seal the terms of His covenant with Adam—contained in Genesis 2:17—by a symbolic and visible emblem ratifying the same; as He did to Noah by the rainbow, and to Abraham by circumcision. With Adam, this confirmatory symbol consisted of “the tree of life” in the midst of the garden. A seal, then, is a divine institution of which it is the design to signify the blessings promised in the covenant, and to give assurance of them to those by whom its terms have been fulfilled. The very name of this symbolic (yet real) tree at once intimated its design: it was “the tree of life.” Not, as some have erroneously supposed, that its fruit had the virtue of communicating physical immortality—as though anything material could do that. Such a gross and carnal conception is much more closely akin to the Jewish and Mohammedan fables, than to a sober interpretation of spiritual things. No, just as its companion (yet contrast) was to Adam “the tree of the knowledge of good and evil” —of “good” while he preserved his integrity and of “evil” as soon as he disobeyed his maker—so this other tree was both the symbol and pledge of that spiritual life which was inseparably connected with his obedience. “It was chiefly intended to be a sign and seal to Adam, assuring him of the continuance of life and happiness, even to immortality and everlasting bliss, through the grace and favor of his Maker, upon condition of his perseverance in his state of innocency and obedience” (M. Henry). So far from its being a natural means of prolonging Adam’s physical life, it was a sacramental pledge of endless life and felicity being secured to him as the unmerited reward of fidelity. It was therefore an object for faith to feed upon—the physical eating to adumbrate the spiritual. Like all other signs and seals, this one was not designed to confer the promised blessing, but was a divine pledge given to Adam’s faith to encourage the expectation thereof. It was a visible emblem to bring to remembrance what God had promised. It is the fatal error of Romanists and other Ritualists that signs and seals actually convey grace of themselves. Not so: only as faith is operative in the use of them are they means of blessing. Romans 4:11 helps us at this point: “And he received the sign of circumcision, a seal of the righteousness of the faith which he had yet being uncircum*cised; that he might be the father of all them that believe, though they be not circumcised; that righteousness might be imputed unto them also.” Unto Abraham, circumcision was both a sign and a seal: a sign that he had previously been justified, and a seal (pledge) that God would make good the promises which He had addressed to his faith. The rite, instead of conferring anything, only confirmed what Abra*ham already had. Unto Abraham, circumcision was the guarantee that the righteousness of faith which he had (before he was circum*cised) should come upon or be imputed unto believing Gentiles. Thus as the rainbow was the confirmatory sign and seal of the covenant promises God had made to Noah, as circumcision was the sign and seal of the covenant promises God had made to Abraham, so the tree of life was the sign and seal of the covenant promises He had made to Adam. It was appointed by God as the pledge of His faithfulness, and as an earnest of the blessings which continued fideli*ty would secure. Let it be expressly pointed out that, in keeping with the distinctive character of this present antitypical dispensation—when the substance has replaced the shadows—though baptism and the Lord’s Supper are divinely appointed ordinances, yet they are not seals unto the Christian. The seal of “the new covenant” is the Holy Spirit Himself (see 2 Cor. 1:22; Eph. 1:13; 4:30)! The gift of the blessed Spirit is the earnest or guaranty of our future inheritance. Found here.