What is the ruling on praying in a prison or in unclean clothes, given the difficulty of purifying them?

Dirt that is not ritually impure, like dust, does not invalidate the prayer when present on the place of prayer or on clothes, as the Prophet (peace be upon him) used to prostrate on dust and mud. However, if the dirt is ritually impure (najāsa), then the purity of the garment and the place is a condition for the validity of the prayer. Prayer is not valid in their presence if one is able to remove them. But if one is unable to remove the impurity or if doing so entails unbearable hardship, then the prayer is valid and does not need to be repeated, based on the Almighty's saying: "We do not burden a soul beyond its capacity."