New International Version
An argument developed between some of John's disciples and a certain Jew over the matter of ceremonial washing.
New King James Version
Then there arose a dispute between some of John’s disciples and the Jews about purification.
[a certain] Jew
Adjective - Genitive Masculine Singular
Strong's 2453: Jewish. From Iouda; Judaean, i.e. Belonging to Jehudah.
At https://biblehub.com/john/3-25.htm, 6 versions use "Jews" and 20 versions use "Jew".
Scrivener's Textus Receptus 1894 and other manuscripts are different:
ἐγένετο οὖν ζήτησις ἐκ τῶν μαθητῶν Ἰωάννου μετὰ Ἰουδαίων περὶ καθαρισμοῦ.
Adjective - Genitive Masculine Plural
Is Jew singular or plural in John 3:25?
Some Greek manuscripts have it singular and some plural.