Ar-Rum 30:8
The verse marks the place of reflection: fī anfusihim — within their own selves.
أَوَلَمْ يَتَفَكَّرُوا۟ فِىٓ أَنفُسِهِم ۗ مَّا خَلَقَ ٱللَّهُ ٱلسَّمَـٰوَٰتِ وَٱلْأَرْضَ وَمَا بَيْنَهُمَآ إِلَّا بِٱلْحَقِّ وَأَجَلٍ مُّسَمًّى ۗ وَإِنَّ كَثِيرًا مِّنَ ٱلنَّاسِ بِلِقَآئِ رَبِّهِمْ لَكَـٰفِرُونَ
Do they not reflect within themselves? God did not create the heavens and the earth, and what is between them, except with reason, and for a specific duration. But most people, regarding meeting their Lord, are disbelievers
Ar-Rum 30:8 · Translation: talal-itani
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Reflection is not only to look outward; to look at one's own body, one's own age, one's own flow is also a field of reflection. The verse completes this inner reflection with a bridge that binds it to the creation of the heavens and the earth: outer cosmos and inner cosmos are alike encircled by the same ḥaqq and the same ajal (appointed term). The measure that holds outside holds inside too.
Observation
Modern cosmology shows that the universe has evolved within an expansion process that began approximately 13.8 billion years ago; the fact that the universe has an age is an established finding of observational astronomy. The fact that stars exhaust their fuel and fade, and that celestial bodies are born and age, is also part of the same observational framework.
Exegesis
Classical exegetes note that fī anfusihim is open to two readings: al-Rāzī says that both "about the creation of their own selves" (a person reflecting on their body, their spirit, their maturation) and "within themselves, in silence" (a seclusion, an inner listening) run together. Al-Qurṭubī observes that "ḥaqq and ajal" in the verse's continuation reminds that both the cosmos and the human have a beginning and an end — that this boundedness is a measure settled within creation. Elmalılı says the verse calls to a personal awakening — reflection must first turn not to distant horizons but to one's own self.
Sources
Tafsīr: al-Rāzī · Mafātīḥ al-Ghayb; al-Qurṭubī · al-Jāmiʿ li-Aḥkām al-Qurʾān; Elmalılı Hamdi Yazır · Hak Dini Kur'an Dili.