Ibn Majah

Benefits and Issues:
(1)
If a woman has been divorced three times and her husband wishes to take her back, this is not permissible for him. At that time, if another man marries this woman, and his intention is not to live a proper marital life with her, but merely to marry her and, after seclusion, divorce her so that the first husband can marry her anew and what was forbidden for him becomes permissible—this temporary marriage is called halalah, which is described in this hadith as an accursed act.

(2)
Intention holds great importance in the Shariah. The Prophetic statement is:
«إِنَّمَا الْأَعْمْالُ بِالنِّیَّات» (Sahih al-Bukhari, Book of Revelation, Chapter: How the Revelation Began to the Messenger of Allah ﷺ... Hadith: 1)
“Actions are judged by intentions.”
Since the purpose of a halalah marriage is not the same as that which is required in a legitimate marriage, therefore, in terms of Shariah, this is not a marriage at all, but rather a legal trick, and this trick is a grave sin.
The prohibition of halalah is established by the curse, because a curse cannot be upon a permissible act.
Referring to the one who performs halalah as a “rented bull” points to the repugnance of this act.
Just as a bull is taken for breeding animals so that it mates and impregnates the female animals, and then is returned to its owner,
similarly, the one who performs halalah is requested by the one seeking halalah to establish a temporary relationship with the woman so that, after seclusion, he divorces her and makes her permissible for the first husband.
Just as the one who rents the bull does not become its owner, likewise, the one who performs halalah does not establish a permanent relationship with the woman, but, in his view, fulfills the need of the husband and then separates from the woman.
In this way, it is a form of unlawful relationship similar to the mut‘ah practiced among the Shia, which is attempted to be legitimized by calling it “marriage.”