The ruling on one who performs wudu' and walks on dry impurity

Question:
The questioner says, O Shaykh: If a person performs wudu' and his feet are wet with water, and he walks on a bed that has dry impurity on it, is he required to wash his feet? And is the prayer valid in a place that has dry impurity?

Answer:
If he walks on dry impurity and his foot is wet, it is obligatory for him to wash it if he passes beyond this point. Likewise, if he walks on a wet place that contains impurity and his foot is dry, but the place is wet and contains impurity, and he steps on it, he must wash his foot as well. Yes.

The presenter: May Allah reward you with good, O Shaykh.