Narrated Anas bin Malik Once the Prophet (p.b.u.h) entered the Mosque and saw a rope hanging in between its two pillars. He said, "What is this rope?" The people said, "This rope is for Zainab who, when she feels tired, holds it (to keep standing for the prayer.)" The Prophet said, "Don't use it. Remove the rope. You should pray as long as you feel active, and when you get tired, sit down."

Narrated 'Aisha: A woman from the tribe of Bani Asad was sitting with me and Allah's Apostle (p.b.u.h) came to my house and said, "Who is this?" I said, "(She is) So and so. She does not sleep at night because she is engaged in prayer." The Prophet said disapprovingly: Do (good) deeds which is within your capacity as Allah never gets tired of giving rewards till you get tired of doing good deeds."