Sunan An-Nasa'i

It was narrated from Anas bin Malik that:The Messenger of Allah (ﷺ) entered the masjid and saw a rope tied between two pillars. He said: ""What is this?"" They said: ""It is for Zainab when she prays; if she gets tired she holds on to it."" The Prophet (ﷺ) said: ""Untie it. Let any one of you pray as long as he has energy, and if he gets tired let him sit down