Hadith #8 (Sahih Muslim)
Book: The Book of Faith
Narrator(s): Abdullah al-Khaulani
Grade: Sahih

Five prayers during the day and the night. (Upon this he said: Am I obliged to say any other (prayer) besides these? He (the Holy Prophet, ) said: No, but whatever you observe voluntarily, out of your own free will, and the fasts of Ramadan. The inquirer said: Am I obliged to do anything else besides this? He (the Holy Prophet) said: No, but whatever you do out of your own free will. And the Messenger of Allah told him about the Zakat (poor-rate). The inquirer said: Am I obliged to pay anything else besides this? He (the Holy Prophet) said: No, but whatever you pay voluntarily out of your own free will. The man turned back and was saying: I would neither make any addition to this, nor will decrease anything out of it. The Prophet remarked: He is successful, if he is true to what he affirms.

Source: https://parallelquran.com/hadith/sahih-muslim-8/

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Hadith #7285 (Sahih Muslim)
Book: The Book of Zuhd and Softening of Hearts
Narrator(s): Abdullah al-Khaulani
Grade: Sahih

You discuss it very much whereas I have heard Allah’s Messenger (ﷺ) as saying: He who builds a mosque– and the narrator Bukair said: I think he also said: (for) seeking the pleasure of Allah- Allah would build (a similar house for him in Paradise). and in the narration of Harun (the words are):” A house for him in Paradise.”

Source: https://parallelquran.com/hadith/sahih-muslim-7285/