Is it permissible for a woman to leave off the mourning period for her husband?

Question:
There are some tribes in the Hijaz, among which I mention: the Thaqif tribe, the Banu Malik tribe, and some of the Banu al-Harith tribe; where the woman among them does not observe the mourning period for her husband upon his death. What is the ruling on this?

Answer:
This is, in any case, a form of ignorance that must be removed through knowledge, whether it is among the Banu Malik, the Thaqif, or others. It is necessary that the callers to Allah and the judges inform the people about this matter which they are ignorant of, which is the non-observance of the mourning period, namely that when a woman’s husband dies, she does not observe the mourning period for him.
The mourning period is the leaving off of adornment, perfume, jewelry, and the like during the waiting period until the waiting period ends. May Allah guide them to this, for it is obligatory that they be informed that the Messenger of Allah (peace and blessings be upon him) commanded the wife to observe the mourning period for four months and ten days. The mourning period is the leaving off of anything that invites to her marriage or makes her desirable, from types of beautification such as beautiful clothes, perfume, jewelry, kohl, and the like. She must also stay in her home during the waiting period until the waiting period for death ends, and if she is pregnant, until she gives birth.

Question: The rest of the question: As the man among them exchanges his sister or daughter for a wife of his, without paying any money, is that permissible? And what is your Eminence’s comment on this?

Answer: This is called: al-shigar, and some people call it marriage by exchange. It is when a person says to another: Marry me your daughter and I will marry you my daughter, or your sister, or your brother’s daughter. This is called marriage by exchange, and it is the marriage of al-shigar.
The Prophet (peace and blessings be upon him) prohibited the marriage of al-shigar in several hadiths. The Messenger of Allah (peace and blessings be upon him) prohibited the marriage of al-shigar, which is when a man says to another: Marry me your daughter, and I will marry you my daughter, or marry me your sister, and I will marry you my sister, or he says: Marry my son, and your son, or my son, and your maternal uncle, or the like of that. This is not permissible; this is an abomination from which one must beware, even if they name a mahr. It is obligatory to beware of this, and that the woman not be the mahr for the other. Rather, this one proposes to her, and this one proposes, so whoever is suitable accepts, and whoever is not does not. As for them agreeing to the exchange, where this one gives his daughter, and this one gives his daughter, or his sister, or his brother’s daughter, meaning his ward, this is not permissible, and the marriage is defective, even if a mahr is named.
Some scholars held that if a mahr is named of equal value, it is valid, but this is the weaker position. The correct view is that it is not permissible to engage in this marriage absolutely, even if a mahr is named.
It is established with Ahmad, Abu Dawud, and others that two men in Medina married each other in al-shigar, and they had named a mahr. This was brought to the Commander of the Faithful, Mu'awiyah (may Allah be pleased with him) , and he wrote to the governor of Medina to separate them, saying: This is the al-shigar which the Prophet (peace and blessings be upon him) prohibited, and they had named a mahr.
As for what is narrated in the hadith of Ibn 'Umar regarding the interpretation of al-shigar, and that it is that in which there is no mahr, this is from the words of Nafi', the narrator from Ibn 'Umar, and a group said: it is from the words of Malik ibn Anas, who is also a narrator.
In any case, this is not from the words of the Prophet (peace and blessings be upon him) interpreting al-shigar as being devoid of mahr; it is not from the words of the Prophet (peace and blessings be upon him), but it is from the words of some of the narrators. The words of a narrator do not constitute a proof; the proof is in the words of the Prophet (peace and blessings be upon him). The Prophet prohibited al-shigar and did not interpret it as the absence of mahr; rather, he interpreted it as when this one says: I marry you my sister, or my daughter, and the other says the same, or says: Marry me and I will marry you. Thus the Prophet (peace and blessings be upon him) interpreted it. This covers both the case where there is a mahr and the case where it is devoid of mahr.