Sunan Abi Dawud Book 5, Hadith 64
The Messenger of Allah (ﷺ) as saying: He who misses him daily round of recital or part of it due to sleep and he recites it between the dawn and the noon prayers, will be reckoned as if he recited it at night.
The Messenger of Allah (ﷺ) entered the mosque (and saw that) a rope tied between two pillars. He asked: What is this rope (for) ? The people told him: This is (for) Hamnah b. Jahsh who prays (here). When she is tired, she reclines on it. The Messenger of Allah (ﷺ) said: She should pray as much as she has strength. When she is tired, she should sit down.
This version of Ziyad has: He said: What is this ? The people told him: This is for Zainab who prays. When she becomes lazy, or is tired, she holds it. He said: Undo it. One of you should pray in good spirits. When he is lazy or tired, he should sit down.
The Prophet (ﷺ) said: Any person who offers prayer at night regularly but (on a certain night) he is dominated by sleep will be given the reward of praying. His sleep will be almsgiving.