From Sahih Bukhari (Hadith 5119):
Salama bin Al-Akwa` said:Allah's Messenger (ﷺ) said, "If a man and a woman agree (to marry temporarily), their marriage should last for three nights, and if they like to continue, they can do so; and if they want to separate, they can do so." I do not know whether that was only for us or for all the people in general. Abu `Abdullah (Al-Bukhari) said: `Ali made it clear that the Prophet said, "The Mut'a marriage has been cancelled (made unlawful)
Reference: Bukhari 5119