John Trapp on John 7:37-40

Verſe 37, 38. In the laſt day] In this eighth day (which the Jews called Hoſanna Rabbah) they read the laſt ſection of the Law, Tremel. ex Talmud. and likewiſe began the firſt; leſt they might otherwiſe ſeem more joyfull in ending their ſections, then willing to begin them. Upon this day alſo, by the inſtitution (ſay they) of Haggai and Zechary, (but more likely, by their own ſuperſtition) they did, with great ſolemnity and joy, Godw. Antiq. Heb. bring great ſtore of water from the River Shiloah to the Temple; where it being delivered unto the Prieſts, it was poured upon the Altar, together with wine; and all the people ſang that of the Prophet Iſa. 12.3. with joy ſhall ye draw water out of the Wels of ſalvation. Hereunto our Saviour is thought to allude, Verſ. 38. Out of his belly ſhall flow Rivers of water; provided, that he beleeve in me, ſo as the Scripture ſaith, he ſhould. For ſo (after Chryſoſtome) Heinſius De-dieu, and others expound it.