Question
If someone mixed their pure clothes with impure clothes and prayed in one of the two garments while being cautious about the impurity of one of them, then wanted to pray again and chose the one he did not pray in?
Answer
I say, and with God's success: It is not correct; because the endorsement of ijtihad (jurisprudential reasoning) is not invalidated by a similar one except in the case of the qibla (direction of prayer); because it can be shifted to another direction through ijtihad; as it is a religious matter, and impurity is a physical matter that cannot be made pure through ijtihad due to the necessity of repeating the prayer if impurity appears after ijtihad in clothing and utensils. Therefore, whenever we consider a garment pure through ijtihad out of necessity, it is not permissible to consider it impure through a similar ijtihad, thus invalidating every prayer performed with what was initially deemed impure, while the prayer is valid with what was deemed pure. See: Maraqi al-Falah, pp. 34-35, and God knows best.