Is the purity of the place of prayer a condition for its validity?
Chapter on Praying with Impurity and Other Matters
Al-Mughni
Book of Prayer
Primary text
The purity of the place of prayer is a condition for its validity. This place is defined as the area where the worshipper's limbs fall and where the garments they are wearing make contact. If a piece of a turban hangs down, and its other end falls onto impurity (najasah), the prayer is not valid. The primary view holds that the purity of the place touched by the garments is essential because the covering (the garment) is subordinate to the worshipper, thus being like the limbs used for prostration.
Supporting text
Ibn Aqil mentioned a possibility that the purity of the area touched only by the garments is not required, because the worshipper is touching it with something separate from their essence, similar to when a person wearing impure clothing stands next to the praying person such that their garments touch.