What is the ruling on touching dry impurity with a wet hand, and does dry oily impurity transfer to a wet hand? What is the ruling on eating non-dry food that has touched dry impurity? Is the persistence of the trace of oily impurity on the hand after washing it excused?

A wet hand becomes impure upon touching dry impurity. The Hanafi school differentiates between "wetness" (rutubah) and "dampness" (nadawah). Wetness, which drips, transmits impurity. However, mere dampness, from which nothing drips, does not transmit impurity, according to the more sound opinion. Similarly, wet food becomes impure if it comes into contact with dry impurity. The lingering smell of impurity on the hand is excused if its removal is difficult after the substance itself has been eliminated.