Does sleeping on a dry impure mattress, with sweat coming from the buttocks during sleep, affect the purity of the body and clothes?

If you doubt the transfer of impurity, it is not transferred by doubt, for the default state is purity. However, if you are certain that a wet, sweat-soaked area of your body touched an impure spot on the bed directly, without a barrier, then it has become impure and must be washed.