Al-Bukhari reported: Ali ibn Abi Talib, may Allah be pleased with him, said, “Set out with the world at your back and the Hereafter at your front. Each of them both has their children. Be children of the Hereafter and not children of the world, for today is for action and not reckoning, while tomorrow is for reckoning and not action.”
Source: Ṣaḥīḥ al-Bukhārī 8/89
عن البخاري وَقَالَ عَلِيُّ بْنُ أَبِي طَالِبٍ رضي الله عنه ارْتَحَلَتِ الدُّنْيَا مُدْبِرَةً وَارْتَحَلَتِ الآخِرَةُ مُقْبِلَةً وَلِكُلِّ وَاحِدَةٍ مِنْهُمَا بَنُونَ فَكُونُوا مِنْ أَبْنَاءِ الآخِرَةِ وَلاَ تَكُونُوا مِنْ أَبْنَاءِ الدُّنْيَا فَإِنَّ اليَوْمَ عَمَلٌ وَلاَ حِسَابَ وَغَدًا حِسَابٌ وَلاَ عَمَلٌ
8/89 صحيح البخاري كتاب الرقاق باب في الأمل وطوله