The World Federation One Stop Fiqh

Ruling 187

If the sun shines on impure earth and afterwards a person doubts whether or not the earth was wet when the sun shone on it, or whether or not the wetness of the earth has dried by means of the sun, then that earth is impure. The same applies if one doubts whether or not the intrinsic impurity has been removed. And if a person doubts whether or not something prevented the sun from shining on the impure object, then to consider it as having become pure is problematic [i.e. based on obligatory precaution, it must not be considered as having become pure].