John 7:38,39 - Joseph Benson’s Commentary on the Old and New Testaments

He that believeth on me With a living faith, and with his heart unto righteousness; as the Scripture hath said As God in the Scriptures hath promised and attested in many places; out of his belly From within him, from his mind and heart; shall flow rivers of living water He shall receive spiritual blessings, or communications of divine grace, in so great an abundance, that he shall not only be refreshed and comforted himself, but shall be instrumental in refreshing and comforting others. The expression, Out of his belly shall flow rivers, is used with allusion to receptacles round springs, out of which great quantities of water flow by pipes: and the figure therefore signifies the plenitude of spiritual gifts and graces to be possessed by believers, and the happy effects which they should produce in the world. Thus the apostles and first messengers of Christ were both watered themselves and enabled to water others, Gentiles as well as Jews, not with small streams, but with large rivers of divine knowledge and grace, so that the countries, which till then had been barren, became exceeding fruitful in holiness and righteousness. Accordingly the evangelist adds, by way of explication, this spake he of the Spirit Of the Holy Spirit's gifts and graces; which they who believed on him should receive Εμελλον λαμβανειν, were about to receive, namely, after the resurrection and ascension of Christ, according to his promise, John 14:16; and John 16:7. The extraordinary gifts of the Spirit had, in a great measure, ceased since the death of Zechariah and Malachi. They had been faintly manifested in the approach of the Messiah, as to Zechariah and Elizabeth, to Simeon and Anna, and especially to John the Baptist, who is said to have been filled with the Holy Ghost from his mother's womb; but the full effusion of these gifts, foretold by Isaiah and Joel, took not place till after the ascension of Christ, and was yet to come. On the day of pentecost, and not before, these extraordinary gifts were communicated to the apostles, evangelists, and many other believers, to fit them for converting the world. The universality, however, of the invitation and promise here given, makes it evident that, on this occasion, our Lord had the ordinary influences of the Spirit in his eye, which the evangelist's remark, that the Holy Ghost was not yet given, will not exclude; because, even these might at that time be said not to have been given, as they had been given but sparingly, in comparison of the plentiful distribution which was to be made of them to all believers after Christ's ascension. Accordingly, the ordinary influences of the Spirit are often in Scripture represented as the consequences and reward of faith, Galatians 3:14; Ephesians 1:12-14.