The Gemoroh states that if a man married a woman who brings in two maidservants and then marries a second wife, he may give one of these maidservants to the new wife.
We learned earlier that the proceeds of a womans work belong to her husband. However, if this woman brought in servants (depending on how many) her workload is lessened.
That being the case, although our Gemoroh explained that the work of the maidservant was for the benefit of the house, this will work out to be a detriment for the first wife!!
S, UK
Thank you for this great question! The Rishonim explain (see Rambam, Hilchos Ishus 22:35) that the rule we learn from this Gemara is that since the servants and slaves the woman brought at the time of the marriage are meant to help the wife do what she is committed to do for her husband, if the husband marries another wife, he may use these servants even while he is with the other wife in her house, because these servants are (also) there for him. Obviously, the husband cannot ask his first wife to cook or wash for him while he is with his second wife, but if the first wife relies on servants, he can ask them to join him even if he is now not with his first wife, who actually provided the servant.
I hope this helps,
Aharon Steiner