Chapter on Temporary Marriage (Mutʿah)
Man Lā Yaḥḍuruh al-Faqīh|Volume 3|Book 3|Chapter 44
وَ قِيلَ لِأَبِي عَبْدِ اَللَّهِ عَلَيْهِ اَلسَّلاَمُ لِمَ جَعَلَ فِي اَلزِّنَا أَرْبَعَةً مِنَ اَلشُّهُودِ وَ فِي اَلْقَتْلِ شَاهِدَيْنِ قَالَ "إِنَّ اَللَّهَ تَبَارَكَ وَ تَعَالَى أَحَلَّ لَكُمُ اَلْمُتْعَةَ وَ عَلِمَ أَنَّهَا سَتُنْكَرُ عَلَيْكُمْ فَجَعَلَ اَلْأَرْبَعَةَ اَلشُّهُودِ اِحْتِيَاطاً لَكُمْ وَ لَوْ لاَ ذَلِكَ لَأُتِيَ عَلَيْكُمْ وَ قَلَّ مَا يَجْتَمِعُ أَرْبَعَةٌ عَلَى شَهَادَةٍ بِأَمْرٍ وَاحِدٍ".
It was said to Abu Abdullah عليه السلام: "Why has Allah سبحانه وتعالى prescribed four witnesses for proving adultery (Zina) and only two witnesses for proving murder?" Imam عليه السلام replied: "Indeed, Allah سبحانه وتعالى, the Blessed and Exalted, has made Mut'ah (temporary marriage) lawful for you, and He سبحانه وتعالى knew that it would be denied and rejected by people. Therefore, He سبحانه وتعالى required four witnesses as a precaution for you. Had it not been for this requirement, people would have accused you unjustly. And it is rare for four people to come together and testify about the same matter."
- Ṣaḥīḥ al-Faqīh