The fourth perek of Massekhet Sota focuses on the question of whether the laws of sota apply to all couples. Among the cases presented in the first Mishna (23b) is the case of an arusa – a woman who is betrothed to her husband (i.e. she is considered married, having received kiddushin from him, but they have not completed the nissu’in and they have not had huppa).
The Gemara brings a series of proof-texts to show the source of this halakha and suggests that the simplest source may be the tradition that Rabbi Aha bar Hanina brought “from the South” – that the passage mibaladei ishekh (see Bamidbar 5:20) teaches that the bitter waters of the sota will only work if the woman has first slept with her husband before transgressing.
Rami bar Hama rejects this as a possible source, pointing to a case where the engaged couple had relations before their marriage. We see, therefore, that it is possible to have a case where an arusa will have slept with her husband before transgressing.
The Rambam teaches that the reason an engaged couple that had relations before completing their marriage cannot participate in the sota ceremony is because the husband also committed a transgression when he had relations with his wife before their marriage was complete. The Ra’avad argues, claiming that this Gemara disproves the Rambam’s thesis, since it is clear according to Rami bar Hama that an arusa who slept with her husband would be eligible to drink the “bitter water” were it not for other sources that forbid her from doing so.
With regard to Rabbi Aha bar Hanina bringing a tradition mi-daroma – “from the South” – apparently this is a reference to the period following the Bar Kokheva revolt when the center of Jewish life moved northward to the Galilee. At that time, only a small number of Jewish communities remained in Judea and the southern part of Israel. These communities retained ancient oral traditions, and it is not unusual for the Gemara to report that a Sage returned from travel to the southern part of Israel with baraitot that were unknown to the Sages of the Galilee.