The most favorable worship is night prayer, where Imam Muslim narrated on the authority of Abu-Hurairah that the Prophet (PBUH) said: (The best fasting after the month of Ramadan is the month of Allah, Al-Muharram, and the best prayer is prayer at night.)

Satan is keen to deviate Muslims from observing night prayer through many means like a Muslim being tired, sickness, elder, or old age, on the pretext that he cannot bear long standing in night prayer. So, the Prophet made it sunnah to perform night prayer sitting in such circumstances to facilitate it to Muslims so that they are encouraged to stand for night prayer. In this regard, Imam Bukhari narrated on the authority of `Aishah who said: (I never saw Allah's Messenger (ﷺ) offering the night prayer while sitting except in his old age and then he used to recite while sitting and whenever he wanted to bow he would get up and recite thirty or forty verses (while standing) and then bow.)

Imam Abu-dawud, ranked sahih by Al-Albani, on the authority of `Aishah who said: (Do not give up prayer at night, for the Messenger of Allah (ﷺ) would not leave it. Whenever he fell ill or lethargic, he would offer it sitting.)

Prophet Muhammad feared extremism in practicing worships lest it leads to abandoning it entirely, so he urged Muslims to sit if they felt fatigue, where Imam Bukhari narrated on the authority of Anas ibn Malik who said: (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 (ﷺ) said, "Don't use it. Remove the rope. You should pray as long as you feel active, and when you get tired, sit down.")

To be honest, I have to mention that the reward of the Muslim praying standing is more than who sits if he does so without palatable excuse. In this regard, Imam Bukhari narrated on the authority of `Emran ibn Hussain who suffered hemorrhoids that he asked the Prophet about the possibility of performing prayers sitting. The Prophet replied: (Whoever performs prayer standing up, that is better. Whoever performs prayer sitting down will have half the reward of one who prays standing. And whoever performs prayer lying down will have half the reward of one who prays sitting)

Accordingly, we should seek moderation concerning this matter, that is the original case of the night prayer is while one is standing up, but if we left fatigue, then we may perform it sitting, and earning half of reward is better than earning no reward entirely.

http://300035.dotdothktrade.tech/en/artical/3407727/sunnah-praying-night-prayers-sitting-down