What is the ruling on the prayer of one who prayed in his sandals, being unaware of the presence of impurity on them, and did not ascertain their purity before the prayer?

Praying in sandals is desirable (mustahabb), as it has been established that the Prophet, peace and blessings be upon him, used to pray in his sandals, and he commanded to act contrary to the Jews who do not pray in their sandals. If their purity is confirmed, then praying in them is permissible by the consensus of Muslims. However, if their impurity is certain, then prayer in them is not valid until they are purified. The correct view is that sandals are purified by rubbing them on the ground, as mentioned in the Sunnah. If you doubt the impurity of the khuff (leather slipper), then praying in it is not disliked. And if you become certain of its impurity after the prayer, there is no need to repeat the prayer according to the correct view. Your prayer is valid, due to your uncertainty about the presence of impurity on the bottom of the sandal. The issue of sandals is among those matters where the rare (nadir) takes precedence over the common (ghalib); for impurity is common to them, but Islamic law has nullified the ruling of the common and affirmed the ruling of the rare out of mercy and ease for the servants.