Al-Kāfi - Volume 5 > Permissible Time Length
Hadith #2

2- مُحَمَّدُ بْنُ يَحْيَى عَنْ أَحْمَدَ بْنِ مُحَمَّدٍ عَنْ مُحَمَّدِ بْنِ إِسْمَاعِيلَ عَنْ أَبِي الْحَسَنِ الرِّضَا (عَلَيْهِ السَّلام) قَالَ قُلْتُ لَهُ الرَّجُلُ يَتَزَوَّجُ مُتْعَةً سَنَةً أَوْ أَقَلَّ أَوْ أَكْثَرَ قَالَ إِذَا كَانَ شَيْئاً مَعْلُوماً إِلَى أَجَلٍ مَعْلُومٍ قَالَ قُلْتُ وَتَبِينُ بِغَيْرِ طَلاقٍ قَالَ نَعَمْ.

2. Muhammad ibn Yahya has narrated from Ahmad ibn Muhammad from Muhammad ibn ‘Isma’il who has said the following: “In response to my question before al-Rida’, ‘Alayhi al-Salam, about the case of a man who marries in the manner of al-Mut‘ah (advantageous marriage) for one year or less or more, he (the Imam) said, ‘It is permissible if it is a known matter for a known number of days.’ I then asked if it terminates without divorce. He (the Imam) said, ‘Yes, it terminates without divorce.”’