This is a reference to a report in Muslim's Ṣaḥīḥ collection indicating that mutʿa remained in effect during the lifetime of the Prophet and Abū Bakr. Hossein Modarressi cites this reference to show the complexity of discussions surrounding the meaning and lawfulness of mutʿa in early Islamic discourse.
This source is part of the Online Companion to Hossein Modarressi, Text and Interpretation: Imam Jaʿfar al-Ṣādiq and His Legacy in Islamic Law (Harvard University Press, 2022).