He who believeth in me. He now points out the manner of coming, which is, that we must approach, not with the feet, but by faith; or rather, to come is nothing else than to believe, at least, if you define accurately the word believe; as we have already said that we believe in Christ, when we embrace him as he is held out to us in the Gospel, full of power, wisdom, righteousness, purity, life, and all the gifts of the Holy Spirit. Besides, he now confirms more plainly and fully the promise which we lately mentioned; for he shows that he has a rich abundance to satisfy us to the full. Out of his belly shall flow rivers of living water. The metaphor appears, no doubt, to be somewhat harsh, when he says that rivers of living water shall flow out of the belly of believers; but there can be no doubt as to the meaning, that they who believe shall suffer no want of spiritual blessings. He calls it living water, the fountain of which never grows dry, nor ceases to flow continually. As to the word rivers being in the plural number, I interpret it as denoting the diversified graces of the Spirit, which are necessary for the spiritual life of the soul. In short, the perpetuity, as well as the abundance, of the gifts and graces of the Holy Spirit, [1] is here promised to us. Some understand the saying -- that waters flow out of the belly of believers -- to mean, that he to whom the Spirit has been given makes a part to flow to his brethren, as there ought to be mutual communication between us. But I consider it to be a simpler meaning, that whosoever shall believe in Christ shall have a fountain of life springing up, as it were, in himself, as Christ said formerly, He who shall drink of this water shall never thirst, (John 4:14;) for while ordinary drinking quenches thirst only for a short time, Christ says that by faith we draw the Spirit, that he may become a fountain of water springing up into everlasting life Still he does not say that, on the first day, believers are so fully satisfied with Christ, that ever afterwards they neither hunger nor thirst; but, on the contrary, the enjoyment of Christ kindles a new desire of him. But the meaning is, that the Holy Spirit is like a living and continually flowing fountain in believers; as Paul also declares that he is life in us, (Romans 8:10,) though we still carry about, in the remains of sin, the cause of death. And, indeed, as every one partakes of the gifts and graces of the Holy Spirit, according to the measure of his faith, we cannot possess a perfect fullness of them in the present life. But believers, while they make progress in faith, continually aspire to fresh additions of the Spirit, so that the first-fruits which they have tasted carry them forward to perpetuity of life. But we are also reminded by it, how small is the capacity of our faith, since the graces of the Spirit scarcely come into us by drops, which would flow like rivers, if we gave due admission to Christ; that is, if faith made us capable of receiving him. As the Scripture saith. Some confine this to the former clause, and others to the latter clause; for my own part, I extend it to the entire scope of the discourse. Besides, Christ does not here, in my opinion, point out any particular passage of Scripture, but produces a testimony drawn from the ordinary doctrine of the Prophets. For whenever the Lord, promising an abundance of his Spirit, compares it to living waters, he looks principally to the kingdom of Christ, to which he directs the minds of believers. All the predictions of living waters, therefore, have their fulfillment in Christ, because he alone hath opened and displayed the hidden treasures of God. The reason why the graces of the Spirit are poured out on him is, that we may all draw out of his fullness, (John 1:16.) Those persons, therefore, whom Christ so kindly and graciously calls, and who wander in every direction, deserve to perish miserably.

Footnotes

1 - "Des dons et graces du Sainct Esprit."

He that believeth on me - He that acknowledges me as the Messiah, and trusts in me for salvation.
As the scripture hath said - This is a difficult expression, from the fact that no such expression as follows is to be found literally in the Old Testament. Some have proposed to connect it with what precedes - "He that believeth on me, as the Old Testament has commanded or required" - but to this there are many objections. The natural and obvious meaning here is, doubtless, the true one; and Jesus probably intended to say, not that there was any particular place in the Old Testament that affirmed this in so many words, but that this was the substance of what the Scriptures taught, or this was the spirit of their declarations. Hence, the Syriac translates it in the plural - the Scriptures. Probably there is a reference more particularly to Isaiah 58:11, than to any other single passage: "Thou shalt be like a watered garden, and like a spring of water whose waters fail not." See also Isaiah 44:3-4; Joel 3:18.
Out of his belly - Out of his midst, or out of his heart. The word "belly" is often put for the midst of a thing, the center, and the heart, Matthew 12:40. It means here that from the man shall flow; that is, his piety shall be of such a nature that it will extend its blessings to others. It shall be like a running fountain - perhaps in allusion to statues or ornamented reservoirs in gardens. in which pipes were placed from which water was continually flowing. The Jews used the same figure: "His two reins are like fountains of water, from which the law flows." And again: "When a man turns himself to the Lord, he shall be as a fountain filled with living water, and his streams shall flow to all the nations and tribes of men" (Kuinoel).
Rivers - This word is used to express abundance, or a full supply. It means here that those who are Christians shall diffuse large, and liberal, and constant blessings on their fellow-men; or, as Jesus immediately explains it, that they shall be the instruments by which the Holy Spirit shall be poured down on the world.
Living water - Fountains, ever-flowing streams. That is, the gospel shall be constant and life-giving in its blessings. We learn here:
1. that it is the nature of Christian piety to be diffusive.
2. that no man can believe on Jesus who does not desire that others should also, and who will not seek it.
3. that the desire is large and liberal - that the Christian desires the salvation of all the world.
4. that the faith of the believer is to be connected with the influence of the Holy Spirit, and in that way Christians are to be like rivers of living water.

He that believeth on me, as the Scripture hath said - He who receives me as the Messiah, according to what the Scripture has said concerning me; my person, birth, conduct, preaching, and miracles, being compared with what is written there as ascertaining the true Messiah. Out of his belly - from his heart and soul; for in his soul shall this Spirit dwell.
Living water - As a true spring is ever supplied with water from the great deep, with which it has communication, so shall the soul of the genuine believer be supplied with light, life, love, and liberty, and all the other graces of the indwelling Spirit, from the indwelling Christ. The Jews frequently compare the gifts and influences of the Holy Spirit to water in general - to rain, fountains, wells, rivers, etc., etc. The Scriptures abound in this metaphor. Psalm 36:8, Psalm 36:9; Isaiah 44:3, Isaiah 44:4; Joel 2:23.

He that believeth on me, as the (k) scripture hath said, out of his belly shall flow rivers of living water.
(k) The scripture being referred to is not found anywhere word for word, but rather Christ seems to be referring to many different places where mention is made of the gifts of the Holy Spirit; see (Joel 2:28-29; Isaiah 44:3) and especially (Isaiah 55:1-13).

He that believeth on me,.... Which explains what is meant by coming to Christ, and drinking; for these acts are no other than for a man to go out of himself to Christ, and live by faith on him, and his grace. To which what follows is a great encouragement;
as the Scripture hath said: some refer these words to the preceding clause concerning believing in Christ, which the writings of the Old Testament speak of, as in Deuteronomy 18:15, and the sense is, that he that believes on Christ, the object of faith the Scripture points at, and in him, as that directs and requires; that believes in him as the mighty God, and as the prophet, priest, and King, and as the only foundation of the church, and lives by faith upon him, as just men do, then
out of his belly shall flow rivers of living water, though rather they belong to what follows; and do not design any particular place of Scripture; for no such one is to be found, where the following passage is expressed in so many words; but all those Scriptures which speak of grace, under the metaphors of water, and abundance of water, as rivers and floods of water, and of the effusion of the Holy Spirit, under such figurative expressions, such as Isaiah 41:17. Hence the Syriac version reads in the plural number, "as the Scriptures hath said"; referring to more than one: "out of his belly shall flow rivers of living water"; the grace of the Spirit of God is signified by water, because it is of a cleansing and purifying nature, as faith and hope are, having to do with the blood of Christ, which cleanses from all sin; and because it fructifies and causes the saints, as trees of righteousness, to grow, and bring forth fruit; and especially because it is cooling to those who are scorched with the heat of a fiery law, and very refreshing to thirsty souls: and it is called "living" water, because by it dead sinners are quickened, drooping saints are revived, and comforted; spiritual life in them is maintained and supported, and it springs up to, and issues in eternal life: and it is expressed by "rivers" of living water, because of the abundance of it in regeneration, justification, and pardon; it is grace for grace, abundance of grace believers receive from Christ; and from him, in whom those large measures of grace are, they "flow out" again, even "out of his belly": from within him, out of his heart, the seat of it, by his lips, both in prayer to God, and in conversation with the saints, to whom he communicates his rich experiences of grace, to their comfort, and the glory of God: for grace is of a diffusive and communicative nature; out of the abundance of the heart, the mouth speaketh: and also it flows out by his life and conversation, which is sober, righteous, and godly; and this the grace of God teaches and influences: and this grace, as it is permanent and lasting itself, even perpetual, and always abiding; so it continues to flow, and to show itself in its acts and effects, in one way or another. The Jews ought not to find fault with Christ's using such expressions, mystically understood, since they, comparing Moses and the Messiah together, say,
"as the first Redeemer caused a well to spring up, so the last Redeemer shall cause waters to spring up, according to Joel 3:18 (e).''
(e) Midrash Kohelet, fol. 63. 2.

as the scripture hath said--These words belong to what follows, "Out of his belly, as the scripture hath said, shall flow," &c. referring not to any particular passage, but to such as Isaiah 58:11; Joel 3:18; Zac 14:8; Ezekiel 47:1-12; in most of which the idea is that of waters issuing from beneath the temple, to which our Lord compares Himself and those who believe in Him.
out of his belly--that is, his inner man, his soul, as in Proverbs 20:27.
rivers of living water--(See on John 4:13). It refers primarily to the copiousness, but indirectly also to the diffusiveness, of this living water to the good of others.

He that believeth on me, as the scripture hath said. Notice that "believing" corresponds to "coming" in the preceding verse, showing that faith is the means that brings us to Christ. The reference is not to any single passage, but to the spirit of the Scripture, notably such passages as Isaiah 55:1; Isaiah 58:11; Psalm 36:8-9.
Out of his belly shall flow rivers of living water. Christ is the living water; he who believes upon Christ has Christ formed within him, and hence must become a fountain to dispense the living water whatever he goes.

He that believeth - This answers to let him come to me. And whosoever doth come to him by faith, his inmost soul shall be filled with living water, with abundance of peace, joy, and love, which shall likewise flow from him to others. As the Scripture hath said - Not expressly in any one particular place. But here is a general reference to all those scriptures which speak of the effusion of the Spirit by the Messiah, under the similitude of pouring out water. Zac 14:8.