Sotah 004

1:
The previous mishnah established that a man who wishes to establish a case for the 'cursing waters' must formally warn his wife. The present mishnah elaborates on this. The husband must instruct his wife in the presence of two witnesses who are competent to testify in a Bet Din [halakhic court of law] that she is not to converse with a certain named individual. However, even though the instruction is not to converse (i.e. speak) with her suspected paramour, the husband cannot take the matter further even if she does speak with that man. The husband will be able to prosecute his case only if two witnesses can testify that she secluded herself with her paramour away from public view for a period of time that is sufficient for sexual intercourse. (Throughout this and subsequent mishnayot the woman who has been unfaithful to her husband is euphemistically described as being 'defiled'.)

2:
Our mishnah also indicates the consequences of the actions of the couple. If the wife only defies her husband's warning by speaking with the man with whom she was warned not to speak, she is still permitted to live conjugally with her husband. The phrase 'permitted to her house' is a euphemistic expression meaning that she is permitted to have normal sexual relations with her husband. If her husband is a kohen [priest] she is also still permitted to eat of his Terumah since she is still his legal wife for all purposes. Only if she is observed secluding herself away from the gaze of others with her suspected paramour for a period of time that would permit the assumption that sexual intercourse may have taken place does she become immediately prohibited to her husband. From that moment on the only way that she can become permitted to him again is by successfully undergoing the test of the 'cursing waters'.

3:
Certain terms used in our mishnah require clarification.

Terumah was originally an amount varying between 1.666% and 2.5% of a farmer's agricultural produce, depending on the farmer's generosity, and was to be set aside as a perquisite for the Kohen [priest] of his choice. Food prepared from this terumah ['donative'] could be eaten only by priests and the members of their household.
The Torah places a duty on a surviving brother to marry his deceased brother's childless widow. Such a union is termed levirate marriage [Yibbum]. ('Levir' is the Latin word for a brother-in-law.) Just as the ceremony of divorce terminates an ordinary marriage, so the ceremony of Ĥalitzah terminates a levirate marriage.

Thus our mishnah is saying that if the husband dies in the period subsequent to the wife being observed with her paramour and before the test of the 'cursing waters' she may not contract a levirate marriage with her brother-in-law if she is childless, but she must give him Ĥalitzah.

Susanna Ruerup writes:

Why in many texts is the word 'rosh' translated as 'hair', as in the torah translation you offered ('...and let the hair of the woman's head go loose"...) and not with 'head'? Did the meaning of the word 'rosh' change during the times or is it a matter of interpretation?

I respond:

Neither! The Hebrew phrase used in the Torah means to let her hair loose by undoing her hairdo. The word 'rosh' [head] is used because it refers to her hair being piled up on her head, as we shall see later on in our study of this tractate. It seems that married women piled their hair up on top of their heads in order that it be constantly covered. This was considered a woman's glory, and a woman who willfully ignored this custom was held to be in breach of 'Jewish Women's Law' [Dat Yehudit]. Part of the process of humiliating the wife suspected of adultery was the undoing her hairdo in public, which was considered to be a terrible breach of common etiquette.