The ruling on using a sutrah for a traveler on a chair and the distance that invalidates the prayer

Question:
May Allah reward you, Honorable Shaykh. This questioner says: If a person prays on a chair due to his inability, does he use a sutrah? And what is the distance that invalidates his prayer?

Answer:
The hadiths are general; whether one prays on a chair or otherwise, he uses a sutrah. The distance between him and the sutrah, as you heard, is the width of a sheep’s passage. Yes. May Allah reward you, sir. If there is a sutrah in front of him, no one passes in front of him within a distance of three cubits; no one passes within this space.