I say, and with God's success: If the garment has two sides, one of which is impure, and he spreads it on the ground and prays on the pure side, it should be noted: if one side is sewn to the other, it is not permissible; because they are considered as one thing. However, if one side is not sewn to the other, it is permissible; because by separating, it becomes like the other. Refer to: Al-Wiqayah p132, and Umdat Al-Ri'ayah 1: 140, and God knows best.