What is the ruling on entering the son's house after swearing not to enter it due to the mother's illness and the son's distress? And what are the implications of this entry?

Most scholars are of the view that breaking an oath occurs even if the prohibited act is done out of forgetfulness. However, another group of scholars holds that there is no breaking of the oath if the act is done out of forgetfulness, and this is the fatwa given. Based on this opinion, you are not required to offer expiation for breaking the oath. However, if expiation becomes necessary, it is to feed ten needy persons, or clothe them, or emancipate a slave, or fast for three days if none of these are available. It is recommended that a person break their oath and do what is better, as the Prophet (peace be upon him) said: "By Allah, if Allah wills, I do not swear an oath and then see something better than it, but that I expiate for my oath and do that which is better, or I do that which is better and expiate for my oath."

It is stressed that the son's wife must respect her mother-in-law, and the mother-in-law must treat her son's wife with kindness and gentleness, for Allah says: "And do good; indeed, Allah loves the doers of good," and He says: "Repel evil with that which is better, and thereupon he between whom and you was enmity [will become] as though he was a devoted friend." And the Messenger of Allah (peace be upon him) said: "Kindness is not found in anything but that it adorns it, and it is not removed from anything but that it disgraces it."