Caution: Translations of Quran and Ḥadīth may lead to possible misapplications and misinterpretations. This site is intended for students of sacred knowledge that are proficient in comprehending classical Arabic and have a strong foundation in Islamic sciences. Also note that religious injunctions rely on several aspects beyond what one may glean through reading individual aḥādīth.
Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
quran:36:68 –

And he to whom We grant long life We reverse in creation; so will they not understand?  

And whomever We give long life, by prolonging his term ˹of life˺, We cause him to regress (nankushu; a variant reading has ˹2nd verbal form˺ nunakkishu, derived from al-tankīs) in creation, that is, in terms of his physical form, so that after having enjoyed strength and youth, he becomes feeble and decrepit. Will they then not understand?, that One Who is able to effect such ˹a state˺ — with which they are familiar — is also able to resurrect, that they might then become believers? (a variant reading ˹for ya‘qilūna, ‘they understand’˺ has ˹the second person plural˺ ta‘qilūna, ‘you understand’).
القرآن:٣٦:٦٨ –

وَمَنْ نُعَمِّرْهُ نُنَكِّسْهُ فِي الْخَلْقِ ۖ أَفَلَا يَعْقِلُونَ  

{ومن نعمِّره} بإطالة أجله {نَنْكُسْهُ} وفي قراءة بالتشديد من التنكيس {في الخلق} فيكون بعد قوته وشبابه ضعيفا وهرما {أفلا يعقلون} أن القادر على ذلك المعلوم عندهم قادر على البعث فيؤمنون، وفي قراءة بالتاء.