How sound is the Hadith: "Any man and woman who agree to be together, their companionship shall be for three nights. Then, if they wish to increase, they may do so; or if they wish to part, they may do so," and what is its interpretation? And is it specific to Muslims or general?

The hadith narrated by Al-Bukhari concerning nikah al-mut'ah (temporary marriage) is abrogated, as 'Ali (may Allah be pleased with him) clarified from the Prophet (peace and blessings be upon him), that he prohibited mut'ah and the meat of domestic donkeys during the time of Khaybar. Nikah al-mut'ah was permissible then prohibited. As for the hadith of Salamah ibn al-Akwa', it means that if nikah al-mut'ah is contracted without a specified term, then it is understood to be for three days and nights, after which the spouses have the option to continue or separate.