Al-Mughira said that the Prophet got up at night to such an extent that his feet became swollen. On being asked why he did this when his former and latter sins had been forgiven him, he replied, “Should I not be a grateful servant?” (Bukhari and Muslim.)
Hadith Referenceمشكوة المصابيح / كتاب الصلاة / 1220
Hadith Gradingالألبانی:مُتَّفَقٌ عَلَيْهِ | زبیر علی زئی:متفق عليه
Hadith Takhrij´تحقيق و تخريج: محدث العصر حافظ زبير على زئي رحمه الله` «متفق عليه، رواه البخاري (4836) و مسلم (79 / 2819)»