When John saw many of the Pharisees and Sadducees coming to WHERE he was baptizing

[TonyChanYT]

NIV Matthew 3:

7 But when he saw many of the Pharisees and Sadducees coming to where he was baptizing, he said to them: “You brood of vipers! Who warned you to flee from the coming wrath?

Actually the word "where" is not in the original Greek.

English Standard Version:

But when he saw many of the Pharisees and Sadducees coming to his baptism,

ἐπὶ αὐτοῦ βάπτισμα

he said to them, “You brood of vipers! Who warned you to flee from the wrath to come?

New American Standard Bible:

But when he saw many of the Pharisees and Sadducees coming for baptism, he said to them, “You offspring of vipers, who warned you to flee from the wrath to come?

It seems that the Pharisees and Sadducees visited John, desiring to be baptized by him.

Pulpit Commentary

The Gospel according to the Hebrews (Resch, 'Agrapha.' p. 343) says that they were in fact baptized, but we can hardly suppose this to have been the case after John's words to them. Observe that the Pharisees, with their self-conscious sanctity, were hardly likely to come to confess their sins, or the Sadducees to even listen to so ascetic a teacher.

Ellicott explained:

It is not easy to enter into the motives which led either of the sects to come to the baptism of John. It may be that they were carried away for a time by the enthusiasm of the people, or sought to guide the movement by controlling it, or to enlist the new teacher on this side or that. Anyhow, there was no repentance, and no confession, and so the Baptist met them with a stern reproof.

The Pharisees and Sadducees wanted to be baptized but John might not have baptized them. Matthew 3:11

“I baptize you with water for repentance."

No repentance, no baptism.