I engaged in Mutah with a lady who is an atheist and required her to recite the Kalma before we consummated the marriage. I forgot this requirement until later, but she did recite it afterwards. Is the marriage valid?
Mut’ah marriage is not allowed with atheist or Mushrik unless and until she believes in Islam or a holy book like Torah or Bible (to be from People of Book). It is not only reciting the Kalma but more importantly believing that No Gods but Allah and Mohammad is His messenger (to be a Muslim), or believing in Judaism or Christianity to be from Ahl al-Kitab. With out that, the marriage is invalid.
Wassalam.