Study Sotah folio 3A with parallel Hebrew-English text, traditional commentary, and modern study tools. Free access to Babylonian Talmud online.
Apparently, both Reish Lakish and Rav Yeimar bar R' Shelemya hold that it is prohibited to issue a warning. Both are of the opinion that the word kinnui is a term for anger. Since causing anger is a negative trait, it follows that it is prohibited to issue a warning.
The Talmud asks: And according to the one who says that it is permitted for him to issue a warning, what is the meaning of the term kinnui? Rav Naḥman bar Yitzḥak says: The term kinnui means nothing other than a term of forewarning, and so it says: “Then YHWH warned [vayekanneh] concerning His land
It is taught in a baraita that R' Meir would say: A person commits a transgression in private and God proclaims about him openly, i.e., in public, that he transgressed, as it is stated concerning a sota, who transgressed in private: “The spirit of jealousy came [avar] upon him” (Numbers 5:14); and
Reish Lakish says: A man commits a transgression only if a spirit of folly [shetut] enters him, as it is stated: “If any man’s wife goes aside [tisteh]” (Numbers 5:12). The word tisteh is written with the Hebrew letter shin, affording an alternative reading of tishteh, which is related to the term
§ The Talmud discusses why the testimony of one witness suffices with regard to defilement. The school of R' Yishmael taught a baraita: For what reason did the Torah deem credible a single witness with regard to the defilement of a sota? It is because there is a basis for anticipating the matter,