Question
How can the impurity stuck to the shoe or sandal be purified if it does not have a substance?
Answer
I say, and with God's success: The impurity in the shoe, if it does not have a substance, like urine, does not leave a trace after drying; it can only be purified by washing. Refer to: Al-Wiqayah and its explanation by Sadr al-Shari'ah, p. 130, and Naf' al-Mufti, p. 137, and God knows best.