Time period.
Useful information: The time period of a temporary marriage must be delineated in a manner which allows no possibility of increase or decrease. According to the Imam al-Rida, '. ..(mut'a must) be a stipulated thing for a stipulated period.' [31] In addition, the Imam was once asked if it is possible to conclude a contact of mut'a for 'one or two hours'. He replied, 'No time limit is understood from "one or two" hours.'
According to al-Shaykh al-Ansari, all of the hadith indicate that it is permissible for the agreed upon time period either to be joined to the moment of concluding the contract or to be postponed. The situation here is the same as with a contract concluded for purposes of rental, since-as was pointed out above-the woman takes on certain legal characteristics of rented property.
In the case of a temporary marriage which begins after a period of postponement, there arises the question of whether or not the woman may marry a second man in the period between the conclusion of the contract and the beginning of the marriage period. Here there are two possibilities: that it is not permitted, because the woman already has a husband; or that it is permitted, because of the existence of all the 'requisites of a contract' and the absence of an impediment. Apparently the ruling here is that a second temporary marriage would be permissible provided that the woman has enough time before the beginning of the first marriage to conclude a second marriage and then to observe her waiting period.