Anas (May Allah be pleased with him) reported: The Prophet (PBUH) came into the mosque and noticed a rope stretched between two poles. He enquired, "What is this rope for?'' He was told: "This is Zainab's rope. When during her voluntary prayer, she begins to feel tired, she grasps it for support". The Prophet (PBUH) said, "Untie it. You should perform prayers so long as you feel active. When you feel tired, you should go to sleep".
[Al-Bukhari and Muslim].
Commentary: This Hadith deals with the following three points:
1. It forbids undue strictness and taking support of anything in the course of Salat.
2. If wrong can be corrected by hand, it must be stopped immediately.
3. One should be moderate in `Ibadah and select such times for optional and voluntary prayers when one feels real pleasure in them.