Is everything dry pure, even if it was previously touched by urine? Is something whose impurity is doubtful considered pure simply because it is dry, unless the impurity is seen on it? Is impurity transferred from a dry impure object to another dry object? And how are clothes and other things purified?

If a pure object becomes defiled, whether it is earth or clothing, it is not purified except by pure water, according to the majority of scholars. They made exceptions for sandals, which are purified by rubbing, and a woman's train (garment), which is purified by the earth. Abu Hanifa and some scholars hold the view that it can be purified by any pure liquid that removes the impurity, such as vinegar. They also added purification by dryness from the sun and wind for the earth. Ibn Taymiyyah is of the opinion that objects other than earth can also be purified by the sun and wind.

As for a dry impure object meeting a dry pure object, it does not defile it by mere contact. The default state of things is purity, and this default state is not abandoned unless impurity is confirmed.