Question:
The Mechaber in Orach Chaim Siman 470 writes that there is an opinion that holds a woman that is a first-born should fast on Taanit bechorot. The Rema adds there that this is not the minhag. The Rema however in seif bet does say that when a Father is himself a first-born and this couple has a son that is also a first-born but still a katan that the mother should fast in place of her son (since the father is already fasting because of himself). Why is it that in this case the Rema says a woman should fast for her son (when the father is unable to do so) but not for herself?
(The M”B in seif katan 9 does write that poskim say the woman doesn’t have to fast in this case as well. However I’m asking according to the Rema himself.)
Answer:
The explanation is apparently that there is no rule whereby “women don’t fast”, but rather the rule is that according to the custom a woman’s first-born status does not obligate a fast.
However, where there a son who is a first-born, the son is obliged a fast – and if the father is fasting for himself, he cannot fast on behalf of his son, and the mother must fast on his behalf.
