This is a reference to reports from Jaʿfar al-Ṣādiq that condemn certain sexual behaviors (e.g., anal intercourse) and clarify the meaning of Q. 2:223: "Your women are a tilth to you, so go unto your tilth as you will." Hossein Modarressi cites this reference in the course of his discussion on the attribution of conflicting legal views to al-Ṣādiq on the subject.
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).