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:39:56 –

Lest a soul should say, "Oh ˹how great is˺ my regret over what I neglected in regard to Allah and that I was among the mockers."  

so apply yourselves to this, before any soul should say, ‘Alas for me (yā hasratā is actually yā hasratī, meaning ‘O regret of mine’) for what I have neglected of my duty to God, in other words, ˹of˺ obedience to Him. Indeed (wa-in: in is softened in place of the hardened form, in other words ˹understand it as˺ wa-innī) I was among those who ridiculed’, His religion and His Book;
القرآن:٣٩:٥٦ –

أَنْ تَقُولَ نَفْسٌ يَا حَسْرَتَىٰ عَلَىٰ مَا فَرَّطْتُ فِي جَنْبِ اللَّهِ وَإِنْ كُنْتُ لَمِنَ السَّاخِرِينَ  

فبادروا قبل {أن تقول نفسٌ يا حسرتى} أصله يا حسرتي، أي ندامتي {على ما فرطت في جنب الله} أي طاعته {وإن} مخففة من الثقيلة، وإني {كنت لمن الساخرين} بدينه وكتابه.