In section 9, Calvin remarks that, in fact, Jesus Christ is clearly referred to by the prophets as Jehovah Tsidkenu - Jehovah our Righteousness. He does this in arguing for Christ's full identity as God, contrary to those who would claim that Jehovah is merely the name for the Father, and does not (and/or cannot) refer to the Son. Calvin writes,
"...nothing clearer can be found than the passage of Jeremiah, that 'this will be the name by which the branch of David will be called, "Jehovah our Righteousness"' (Jer. 23:5-6; cf. 33:15-16). For, since the Jews teach that the other names of God are nothing but titles, but that this one alone [Jehovah], which they speak of as ineffable, is a substantive to express his essence, we infer that the only Son is the eternal God who elsewhere declares that he will not give his glory to another. [Isa. 42:8]." (p. 132, Institutes of the Christian Religion)Christ, the branch of David, universally accepted as such, IS - by clear witness of the Scriptures internally referencing themselves, God almighty - Jehovah.
In another place, another strong indicator that Calvin discusses is the identity of the Lord of Hosts - again, unquestionably a title connected with the Almighty, Eternal God.
"For when Isaiah prophesies that the Lord of Hosts is to be 'a stone of stumbling and a rock of offense for the Judeans and Israelites' [Isa. 8:14], Paul declares this prophecy fulfilled in Christ [Rom. 9:32-33]. Therefore he proclaims Christ to be the Lord of Hosts." (p. 134, Institutes of the Christian Religion)Finally, we should easily recognize the divinity of Christ at times when the Jews wished to stone Him for blasphemy - when He claimed to be God. Contrary to many moderns who claim Jesus never laid claim to divinity, He most CERTAINLY did. Witness Calvin's discussion:
"...he not only participates in the governing the world with the Father; but he carries out the other individual offices, which cannot be communicated to the creatures. The Lord proclaims through the prophet, 'I, even I, am the one who blots out your transgressions for my own sake,' [Isa. 43:25] According to this saying, when the Jews thought that wrong was done to God in that Christ was remitting sins, Christ not only asserted in words, but also proved by a miracle, that this power belonged to him. [Matt. 9:6] We therefore perceive that he possesses not the administration merely but the actual power of remission of sins, which the Lord says will never pass from him to another. What? Does not the searching and penetrating of the silent thoughts of hearts belong to God alone? Yet Christ also had this power [Matt. 9:4; cf. John 2:25]. From this we infer his divinity." (p. 136, Institutes of the Christian Religion)Christ is God - a central doctrine of our faith, and one which is under assault today as it has always been, even from those who claim to be Christians. In the remainder of chapter 13 of Book I, Calvin establishes the divinity of the Holy Spirit and then goes on to lay out the distinctions between these three persons of the Triune God. His summary in section 20 is succinct and complete - and should be held sufficient by all to describe the Trinity. No need for illustrations that make the Trinity manageable - just say what Scripture says. This Calvin does wonderfully:
"20. THE TRIUNE GODChapter 13 is worth taking the time to work through. Calvin's treatment of the orthodox doctrine of the Trinity therein is worth reading more than a few times - he deals with the prevalent historical errors he faced in his time, and, lo and behold, the same errors abound today, whether we're talking Oneness Pentecostals or modern liberals - Calvin dealt with and dispensed with their positions tidily.
Therefore, let those who dearly love soberness, and who will be content with the measure of faith, receive in brief form what is useful to know: namely, that, when we profess to believe in one God, under the name of God is understood a single, simple essence, in which we comprehend three persons, or hypostases. Therefore, whenever the name of God is mentioned without particularization, there are designated no less the Son and the Spirit than the Father; but where the Son is joined to the Father, then the relation of the two enters in; and so we distinguish among the persons. But because the peculiar qualities in the persons carry an order within them, e.g., in the Father is the beginning and the source, so often as mention is made of the Father and the Son together, or the Spirit, the name of God is peculiarly applied to the Father. In this way, unity of essence is retained, and a reasoned order is kept, which yet takes nothing away from the deity of the Son and the Spirit. Certainly, since we have already seen that the apostles declared him to be the Son of God whom Moses and the prophets testified to be Jehovah, it is always necessary to come to the unity of essence. Thus we regard it a detestable sacrilege for the Son to be called another God than the Father, for the simple name of God admits no relation, nor can God be said to be this or that with respect to himself.
Now, that the name of Jehovah taken without specification corresponds to Christ is also clear from Paul’s words: “Three times I besought the Lord about this” [2 Corinthians 12:8]. When he received Christ’s answer, “My grace is sufficient for you,” he added a little later, “That the power of Christ may dwell in me” [2 Corinthians 12:9]. For it is certain that the name “Lord” was put there in place of “Jehovah,” and thus it would be foolish and childish so to restrict it to the person of the Mediator, seeing that in his prayer he uses an absolute expression which introduces no reference to the relationship of Father and Son. And we know from the common custom of the Greeks that the apostles usually substitute the name [Lord] for Jehovah. And to take a ready example, Paul prayed to the Lord in no other sense than that in which Peter cites the passage from Joel "Whoever calls upon the name of the Lord shall be saved” [Acts 2:21; Joel 2:32]. Where this name is expressly applied to the Son, we shall see in its proper place that the reason is different. For the present, it is enough to grasp that when Paul calls upon God in an absolute sense he immediately adds the name of Christ. Even so, Christ himself calls God in his entirety “Spirit” [John 4:24]. For nothing excludes the view that the whole essence of God is spiritual, in which are comprehended Father, Son, and Spirit. This is made plain from Scripture. For as we there hear God called Spirit, so also do we hear the Holy Spirit, seeing that the Spirit is a hypostasis of the whole essence, spoken of as of God and from God." (p. 144-145, Institutes of the Christian Religion)