Is it necessary to step out of the bathroom onto a pure rug after performing ablution (wudu'), or is it permissible to place one's foot on any dry spot, even if it was previously impure and then dried?

A person performing ablution is not required to place a mat at the bathroom door. Rather, he performs ablution, exits, and steps on any available clean spot, unless it is impure. If it is impure, he should avoid it by wearing sandals. If he steps on an impure spot before his foot dries, it becomes impure, but it will be purified by touching anything else thereafter. Imam Malik was asked about a man who performs ablution and then steps on a dry, filthy spot. He replied: "There is no harm in that. Allah has made things easy for this Ummah."