Is a wet foot rendered impure if it touches a dry carpet that has dry urine on it? Is this impurity excusable? If one becomes aware of it, is the impurity transferred to clothing by sweat when sitting on a floor that has been walked upon by the wet, impure foot also excusable? Does ceramic purify the foot?

The transference of ritual impurity (najasa) from an impure carpet to the foot, and then to a pure place, is a matter of scholarly disagreement. It is permissible to adopt the opinion that it does not transfer in cases of hardship or obsessive doubt (waswasa). If the foot becomes impure with certainty, it must be washed with water to purify it for prayer, and it is not purified by walking. It is advisable to disregard obsessive doubts and not to rule something as impure except with absolute certainty. As for water separated after purifying impurity, it has a specific ruling.