The prohibition of overburdening oneself in worship

It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her) that she said: "The most beloved and dearest of deeds to the Messenger of Allah (peace and blessings be upon him) was the deed which a servant does constantly and performs with steadfastness, even if it is small in amount."
Musnad al-Harith (Bughyat al-Bahith): 604; the basis of this hadith is also found in Sahih al-Bukhari and Sahih Muslim.

It is narrated from a man of the people of Kufah who was called Jabalah that in the blessed time of the Prophet (peace and blessings be upon him) a young man devoted himself entirely (to intense devotion). So his father came to the Prophet (peace and blessings be upon him) and said: "(O Messenger of Allah (peace and blessings be upon him)!) My son has put himself into severe hardship and exhaustion through excessive worship." The Prophet (peace and blessings be upon him) said: "Instruct him to be gentle with himself (and adopt moderation)."
This report is mentioned in Sunan al-Darimi, and its text teaches balance and moderation in religion instead of extremism and excessive severity, so that a person does not become weary and end up deprived of worship.

It is narrated from Sayyiduna Mihjan bin al-Adra' (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) received news that a man in the mosque was greatly prolonging his (voluntary) prayer. So he (peace and blessings be upon him) came to him, then he (peace and blessings be upon him) took hold of him by the shoulder and said: "Indeed Allah Almighty is pleased with ease and facility for this Ummah and dislikes hardship and difficulty for it." He (peace and blessings be upon him) said these words three times (and further said): "And surely this man has taken up severity and difficulty and abandoned ease." Then he (peace and blessings be upon him) pulled him forcefully towards himself (as a warning), after which that man was not seen again (prolonging the prayer excessively in this way).
Takhrij and grading: The chain of this hadith is jayyid (good). Imam Ahmad narrated it in 'al-Musnad' (19003) and Imam al-Bayhaqi in 'al-Sunan al-Kubra' (3826).

It is narrated from Sayyiduna Abu Musa (may Allah be pleased with him) that the wife of Sayyiduna Uthman bin Maz'un (may Allah be pleased with him) came to the pure wives of the Prophet (peace and blessings be upon him), and they saw her in a very shabby and dishevelled state, upon which they asked her: "There is no man in Quraysh more prosperous and wealthy than your husband (so why is your condition like this)?" She replied: "We get nothing from him (as a husband); his condition is that he fasts all day and stands in prayer all night." The narrator said: Then the Prophet (peace and blessings be upon him) came in, and the pure wives mentioned this matter to him (peace and blessings be upon him). So the Prophet (peace and blessings be upon him) met Sayyiduna Uthman (may Allah be pleased with him) and said: "O Uthman! Do you not have in my life an example and the best model?" He submitted: "O Messenger of Allah (peace and blessings be upon him)! May my father and mother be sacrificed for you, (what fault have I committed)?" He (peace and blessings be upon him) said: "You fast all day and stand in prayer all night, while your wife has a right over you and your own body has a right over you. So pray (at night) and also sleep, and sometimes fast and sometimes leave fasting." The narrator relates that after this guidance that woman came to the pure wives again, perfumed and adorned like a bride. They asked (in astonishment): "Well! What is this?" She replied: "We too have attained the marital comfort and contentment that (ordinary) people enjoy."
Musnad Abi Ya'la: 607. Its chain is hasan (good), and the basis of this incident is also found in Sahih al-Bukhari (5063).

It is narrated from al-Hasan al-Basri (may Allah have mercy on him) that the Commander of the Believers, Sayyiduna Umar bin al-Khattab (may Allah be pleased with him), said: "When one of you stands at night (for the Tahajjud prayer) and the words of the Qur'an become heavy upon him (due to being overcome by sleep, that is, his tongue begins to falter and he does not know what he is reciting), then let him sleep."
I (Ibn Hajar) say: The chain of this report is munqati' (broken); however, its basis is found in the two Sahihs (Bukhari and Muslim).