Theorema de sacramentorum nucleo

Exod. 31:13 and following. If it also represented the mysteries of the Sabbath of Creation, of our Redemption, and of the rest of Christ in the sepulcher: and of our sabbathism and rest in the heavenly fatherland: who now would doubt that it was both a Sacrament and that its nucleus was and is Jesus Christ, who alone is the sponsor of the covenant of grace, and will introduce us into eternal rest?

XXII. Water flowing from the Rock.

10. It is established that Moses, by the command of Iehouah the LORD, struck the rock so that he might obtain water for the people suffering from τῇ ἀνυδρίᾳ the waterlessness. We read that this was done twice. First, indeed, not without notable confidence, in Rephidim, when the rod struck the rock Horeb: Exod. 17:6. Then, however, not without diffidence, in the desert of Sin in that place which was called Kadesh: Num. 20:10-12. This, therefore, is sought, Whether those Rocks, and the waters flowing from them, had the evident nature of a Sacrament, so that Jesus Christ could be called their nucleus?

Response. Paul says: And all drank the same spiritual drink. For they drank from the following spiritual Rock. The Rock was Christ. 1 Cor. 10:4. Why this? (says Bertram) Because in those corporeal substances resided the spiritual power of the TRUTH, which fed the minds of the believers rather than their bodies.

Furthermore, these words, "The Rock was Christ," Augustine explains in Epistle 102 as follows: Sometimes the thing that signifies takes the name of the thing that it signifies. Thus also the Rock is Christ, because it signifies Christ. The same person, so as not to leave room for a sophistry which imagines that the Apostle was not also speaking about the Sign, interprets it in Ps. 77: The spiritual Rock, not Christ Himself: but that which signifies something spiritual.

The same in Lev. Q. 57: Things that signify are wont to be called by the name of the thing they signify. As it is written: Seven ears are seven years. For he did not say, it signifies seven years. And seven oxen are seven years, and many things of this kind. Hence it is that it was said: The Rock was Christ. For he did not say, the Rock signifies Christ: but as if this were what it was, which indeed by substance was not this, but by signification.