I say, and with God's success: There is doubt about its purification for the event, not in its purity, meaning it is not ruled to be pure or impure regarding the event; it is doubtful in its purification for the event. If one does not find water other than it, he should perform ablution with it and then perform dry ablution (tayammum), and whichever he performs first is permissible. However, it is permissible to remove real impurity from the garment and the body with it; because it is pure, and the doubt was only in its purification for the event. The reason for the doubt is the conflicting evidence regarding the domestic donkey, and the original ruling for animals is to be treated like the mother. Refer to: Talweeh on Tadhreeh 2: 210, Maraqi al-Falah p. 28, Nafa' al-Mufti wa al-Sail p. 26, and Kanz al-Daqaiq p. 5, and God knows best.