Regarding contemplating the greatness of Allah's creation, the fleeting nature of this world, the terrors of the Hereafter, and all related matters, as well as the self's shortcomings, disciplining it, and guiding it toward righteousness.
Allah the Exalted said, "I only admonish you with one thing: that you stand up for Allah, in pairs or individually, and then reflect" [Saba 46].
And He the Exalted said, "Indeed, in the creation of the heavens and the earth and the alternation of the night and the day are signs for those of understanding. Who remember Allah while standing, sitting, and lying on their sides and reflect upon the creation of the heavens and the earth, (saying): 'Our Lord, You have not created this aimlessly; exalted are You'" [Al Imran 190, 191].
And He the Exalted said, "Do they not look at the camels, how they are created? And at the sky, how it is raised up? And at the mountains, how they are set up? And at the earth, how it is spread out? So remind, [O Muhammad]; you are only a reminder" [Ghashiyah 18-21].
And He the Exalted said, "Have they not traveled through the earth and observed" [Muhammad 10]. There are many such verses in this regard.
Among the hadiths is the previous one: "The wise one is the one who holds himself accountable."
في التفَكُّر في عظيم مخلوقات الله تَعَالَى وفناء الدنيا وأهوال الآخرة وسائر أمورهما وتقصير النفس وتهذيبها وحملها عَلَى الاستقامة
قَالَ اللَّه تَعَالَى: ﴿إِنَّمَا أَعِظُكُمْ بِوَاحِدَةٍ أَنْ تَقُومُوا لِلَّهِ مَثْنَى وَفُرَادَى ثُمَّ تَتَفَكَّرُوا﴾ [سبأ: ٤٦]
وَقالَ تَعَالَى: ﴿إِنَّ فِي خَلْقِ السَّمَاوَاتِ وَالْأَرْضِ وَاخْتِلافِ اللَّيْلِ وَالنَّهَارِ لَآياتٍ لِأُولِي الْأَلْبَاب الَّذِينَ يَذْكُرُونَ اللَّهَ قِيَامًا وَقُعُودًا وَعَلَى جُنُوبِهِمْ وَيَتَفَكَّرُونَ فِي خَلْقِ السَّمَاوَاتِ وَالْأَرْضِ رَبَّنَا مَا خَلَقْتَ هَذَا بَاطِلًا سُبْحَانَكَ﴾ الآيات [آل عمران: ١٩٠،١٩١] .
وَقالَ تَعَالَى: ﴿أَفَلا يَنْظُرُونَ إِلَى الْأِبِلِ كَيْفَ خُلِقَتْ وَإِلَىالسَّمَاءِ كَيْفَ رُفِعَتْ وَإِلَى الْجِبَالِ كَيْفَ نُصِبَتْ وَإِلَى الْأَرْضِ كَيْفَ سُطِحَتْ فَذَكِّرْ إِنَّمَا أَنْتَ مُذَكِّرٌ﴾ [الغاشية: ١٨، ١٩، ٢٠،٢١]
وَقالَ تَعَالَى: ﴿أَفَلَمْ يَسِيرُوا فِي الْأَرْضِ فَيَنْظُرُوا﴾ الآية [محمد:١٠] والآيات في الباب كثيرةٌ.
ومِنْ الأحَاديث الحديث السَّابق: «الْكَيِّس مَنْ دَانَ نَفْسَه».
from the Prophet ﷺ who said, "The wise person is the one who subdues his ˹lower desires˺ and strives toward what is after death. And the weak-˹minded˺ person (a fool) is the one who follows his desires yet holds hope in ˹a reward˺ Allah."
عَنِ النَّبِيِّ ﷺ قَالَ: «الْكَيِّسُ مَنْ دَانَ نَفْسَهُ وَعَمِلَ لِمَا بَعْدَ الْمَوْتِ وَالْعَاجِزُ مَنْ أَتْبَعَ نَفْسَهُ هَوَاهَا وَتَمَنَّى عَلَى اللَّهِ۔»