John Calvin on John 7:35-36

35. Whither will he go? This was added by the Evangelist, for the express purpose of showing how great was the stupidity of the people. Thus not only are wicked men deaf to hear God’s instruction, but even dreadful threatenings are allowed by them to pass by in mockery, as if they were listening to a fable. Christ spoke expressly of the Father, but they remain fixed on the earth, and think of nothing else than a departure to distant countries.

Will he go to the dispersion of the Greeks? It is well known that the Jews gave the name of Greeks to all nations beyond the sea; but they do not mean that Christ will go to the uncircumcised nations, but to the Jews, who were dispersed through the various countries of the world. For the word dispersion would not apply to those who are natives of the place, and who inhabit their native soil, but applies well to the Jews, who were fugitives and exiles. Thus Peter inscribes his First Epistle παρεπιδήμοις διασπορᾶς, to the strangers of the dispersion, that is, to the strangers who are scattered “Aux estrangers qui estes espars.” through Pontus, Galatia, Cappadocia, Asia, and Bithynia, (1 Peter 1:1;) and James salutes the twelve tribes ἐν τὣ διασπορᾷ, in the dispersion, that is, scattered abroad, (James 1:1.) The meaning of the words therefore is, “Will he cross the sea, to go to Jews who dwell in a world unknown to us?” And it is possible that they intended to teaze Christ by this mockery. “If this be the Messiah, will he fix the seat of his reign in Greece, since God has assigned to him the land of Canaan as his own habitation?” But however that may be, we see that the severe threatening which Christ had uttered did not at all affect them.

John 7:37-39

37. Now on the last day, which was the greatest day of the feast, Jesus stood, and exclaimed, saying, If any man thirst, let him come to me, and drink. 38. He who believeth in me, as the Scripture saith, out of his belly shall flow rivers of living water. 39 But this he spoke of the Spirit which they who believed in him were to receive. For the Holy Spirit was not yet given, because Jesus was not yet glorified.