Shaykh Tusi Said Imam Ali (as) Forbade Muta under Taqiyyah

In many of these sources, and in Shi'i sources as well, the words: 'on the day of the Battle of Khaybar' are added. The Shi'i report that the great Shi'i ulama' such as al-Shaykh al Tusi considered this saying authentic but maintained that 'Ali was practicing taqiyya or 'dissimulation' when he uttered it-i.e., he was hiding the true situation in order to protect himself. (Wasa'il, IV, 441, hadith 32.) http://www.al-islam.org/muta-temporary-marriage-in-islamic-law-sachiko-murata/legitimacy-muta#footnote31_i9ixbxm