Bismillah.
وَاللَّهُ خَلَقَكُمْ ثُمَّ يَتَوَفَّاكُمْ ۚ وَمِنكُم مَّن يُرَدُّ إِلَىٰ أَرْذَلِ الْعُمُرِ لِكَيْ لَا يَعْلَمَ بَعْدَ عِلْمٍ شَيْئًا ۚ
إِنَّ اللَّهَ عَلِيمٌ قَدِيرٌ
Allah has created you, then He takes you away, and there are some among you who are relegated to the feeblest stage of life, so that he knows nothing after having some knowledge. Indeed, Allah is all-knowing, all-powerful.
(Sūrat al-Nahl, No. 16, Āyat 70)
This verse states that the life of the human being and its different stages are in the hands of Allah ‘azza wajall. People die at different ages. Some leave the earth young, others go at a later stage, and some reach an old age where they lose the intellectual capacity that they once possessed. It is a humbling thought that no matter how accomplished and knowledgeable you are, age can take that away from you. It is only God who decides how and when we go.
The word ‘ardhal’ refers to something that is most lowly and base. Here it refers to senility, when a person’s cognitive faculties decline. The human being returns to the original stage of life when there was little knowledge and awareness. Human life begins with weakness in childhood and ends with weakness in old age. We read in Sūrat Yāsīn:
وَمَن نُّعَمِّرْهُ نُنَكِّسْهُ فِي الْخَلْقِ ۖ أَفَلَا يَعْقِلُونَ
And whomever We give a long life, We cause him to regress in creation. Then, will they not exercise their reason? (Q 36:68).
At another place Allah subhānahu wata‘ālā says:
اللَّهُ الَّذِي خَلَقَكُم مِّن ضَعْفٍ ثُمَّ جَعَلَ مِن بَعْدِ ضَعْفٍ قُوَّةً ثُمَّ جَعَلَ مِن بَعْدِ قُوَّةٍ ضَعْفًا وَشَيْبَةً ۚ يَخْلُقُ مَا يَشَاءُ ۖ وَهُوَ الْعَلِيمُ الْقَدِيرُ
It is Allah who created you from [a state of] weakness, then He gave you power after weakness. Then, after power, He ordained weakness and old age: He creates whatever He wishes, and He is the All-knowing, the All-powerful (Q 30:54).
The cognitive decline differs from person to person. For some it starts earlier than others. Also, senility and forgetfulness that creeps in during old age does not apply to everyone. When God wishes, the person remains fully cognizant till the end. This is especially true for the representatives of Allah. Agha Muhsin Qarā’atī in Tafsīr Nūr brings up the example of Prophet Nūh (a) who reached old age and was still able to preach God’s word.
Human beings think their abilities are due to their own efforts and that they themselves are in control. But this verse is a stark reminder that life and knowledge are linked to the power of God. Otherwise, human beings could have preserved it for themselves. The blossoming of human potential at a certain age in the form of knowledge and awareness is by the power of Allah (swt). It will go if God chooses senility for a person at old age.
Believers are advised to keep this reality in mind. It is imperative to make the most of the time when cognitive faculties are still strong. As the Prophet sallallāhu ‘alayhi wa-ālihi wasallam advised Abū Dharr: Oh Abu Dharr! Take advantage of five things before five things seize you: Your youth before your old age, your health before your sickness, your wealth before your poverty, your spare time before your being busy and your life before your death.
May the Almighty help us to be from those who make the most of time before senility and old age.
Sources: Allāmah Muhammad Husayn Tabātabā’ī, Tafsīr al-Mīzān
Agha Muhsin Qarā’atī, Tafsīr Nūr
https://www.al-islam.org/articles/advice-prophet-s-gave-abu-dharr