before his physical departure from this world:

‌لَا ‌يَمُوتَنَّ ‌أَحَدٌ ‌مِّنْكُمْ ‌إِلَّا وَهُوَ يُحْسِنُ بِاللهِ الظَّنَّ

“Certainly, none of you should die except that he has a good opinion of Allah Almighty.”^[1]

We do not know when we will die, it could come at this very moment, tomorrow or in many years-time, and our beloved Prophet صَلَّى اللهُ عَلَيْهِ وَاٰلِهٖ وَسَلَّم instructed us to have a good opinion of Allah Almighty at the time of death, so this means that we must have a good opinion of Allah Almighty in every moment!

Having a bad opinion is a cause of ruin

It one narration, the beloved Prophet صَلَّى اللهُ عَلَيْهِ وَاٰلِهٖ وَسَلَّم said, “None of you should die except that he has a good opinion of Allah Almighty.” He               صَلَّى اللهُ عَلَيْهِ وَاٰلِهٖ وَسَلَّم then mentioned, “There was a nation who was destroyed due to having a bad opinion of Allah Almighty. Allah Almighty said to them:^[2]

وَ ذٰلِکُمْ ظَنُّکُمُ الَّذِیْ ظَنَنْتُمْ بِرَبِّکُمْ اَرْدٰىکُمْ فَاَصْبَحْتُمْ مِّنَ الْخٰسِرِیْنَ (۲۳)

And that was your assumption which you believed about your Lord, it ruined you, so you became among the losers.^[3]

It is stated in Tafsīr Ṣirāṭ al-Jinān that:

We learn that having a bad opinion of Allah Almighty is the way of non-Muslims, and the one who has a bad opinion will be from among those who are ruined and face loss.^[4]