Imām Abū al-Farj Ibn al-Jawzī [d. 510 AH] said:

Indeed, I have seen that the majority of mankind, when afflicted with sickness, busy themselves with grief, despair, and complaints, while others seek medication. They do this until [their sickness] intensifies to the point where its seriousness consumes them, turning their attention away from that which is beneficial to them from:

• [Writing their] last will and testaments.
• Carrying out acts of obedience.
• Preparing for their eventual demise.
• For how many sins have they left unrepented?
• How many borrowed assets have they left unreturned?
• How many debts or zakāh have they left unpaid?
• How many injustices are they responsible for that have been left unfulfilled?

Rather, their only source of despair is separation from this worldly life. As they have no concern besides it. [Their obsession with this dunyā] may even drive them in their waking hours to write their will unjustly.

The reason for this is weakness of īmān, as the Exalted in Might said:

‘Therefore, turn away [O Muḥammad may the peace and blessings of Allāh be upon him] from the one who turns his back on our Reminder —[this Qurʾān] —and desires not except the worldly life. That is their extent of knowledge, [to pursue the world while ignoring the hereafter].’
[Al-Najm, 53:29-30]

This [verse] encompasses most of the creation; we seek refuge in Allāh from abandonment!

Thus, it is most appropriate for the wakeful to make preparations while in good health, before sickness attacks. As they may find their remaining time insufficient for [the necessary] actions to be undertaken, or the realisation of that which has escaped them, or [the writing of] their final testament.

Source: al-Thabāt: 43
Translated by: Riyāḍ al-Kanadī