The first Mishna in Massekhet Sota opens with the words hamekanneh le-ishto – one who issues a warning to his wife – describing the process of a husband warning his wife, in front of witnesses, not to be secluded with a specific man, a process that will lead to her drinking the bitter water of sota if she does so.
As Rashi explains, the term hamekanneh is based on the pasuk (Bamidbar 5:14) that describes the husband’s concern using the words, “Vekinneh et ishto”. Nevertheless, the definition of the word kinneh is not simple, since we find it used with two different meanings. Generally speaking, the usage “kinneh be-…” is understood to mean jealousy – a desire for something that is owned by another that a person wants to have (see Mishlei 24:1, 19). The usage “kinneh le-…” however, is understood to indicate a protective love, anger at someone who injures or tries to attack something that is important to the mekanneh (see, for example, Eliyahu’s argument kano kinneti la-Shem in I 19:10, 14).
The common ground between these two meanings may be the heartfelt emotion that is caused by another. The kinn’ah that is discussed in Massekhet Sota is of the latter type, although, as our Gemara points out, the root word may also be used here meaning a warning, as in the passage, “Ke-ish milhamot ya’ir kinn’ah, yari’a af yatzri’ah” (Yeshayahu 42:13) describing God as shouting during warfare. This is the approach of the Rambam in his Commentary to the Mishna; the Tosefot Yom Tov suggests that in our context the term may refer to anger. In truth, the interpretation of the term is dependent on the dispute on the next page as to whether it is proper for a suspicious husband to issue a warning to his wife.