Messenger of Allah ﷺ said, "It is not permissible for any Muslim who has something to will to stay for two nights without having his last will and testament written and kept ready with him."  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ مَا حَقُّ امْرِئٍ مُسْلِمٍ لَهُ شَىْءٌ يُوصِي فِيهِ يَبِيتُ لَيْلَتَيْنِ إِلاَّ وَوَصِيَّتُهُ مَكْتُوبَةٌ عِنْدَهُ  

The Prophet ﷺ drew a few lines and said, "This is (man's) hope, and this is the instant of his death, and while he is in this state (of hope), the nearer line (death) comes to Him."  

خَطَّ النَّبِيُّ ﷺ خُطُوطًا فَقَالَ هَذَا الأَمَلُ وَهَذَا أَجَلُهُ فَبَيْنَمَا هُوَ كَذَلِكَ إِذْ جَاءَهُ الْخَطُّ الأَقْرَبُ  

The Prophet ﷺ drew a square and then drew a line in the middle of it and let it extend outside the square and then drew several small lines attached to that central line, and said, "This is the human being, and this, (the square) in his lease of life, encircles him from all sides (or has encircled him), and this (line), which is outside (the square), is his hope, and these small lines are the calamities and troubles (which may befall him), and if one misses him, an-other will snap (i.e. overtake) him, and if the other misses him, a third will snap (i.e. overtake) him."  

خَطَّ النَّبِيُّ ﷺ خَطًّا مُرَبَّعًا وَخَطَّ خَطًّا فِي الْوَسَطِ خَارِجًا مِنْهُ وَخَطَّ خُطُطًا صِغَارًا إِلَى هَذَا الَّذِي فِي الْوَسَطِ مِنْ جَانِبِهِ الَّذِي فِي الْوَسَطِ وَقَالَ هَذَا الإِنْسَانُ وَهَذَا أَجَلُهُ مُحِيطٌ بِهِ أَوْ قَدْ أَحَاطَ بِهِ وَهَذَا الَّذِي هُوَ خَارِجٌ أَمَلُهُ وَهَذِهِ الْخُطُطُ الصِّغَارُ الأَعْرَاضُ فَإِنْ أَخْطَأَهُ هَذَا نَهَشَهُ هَذَا وَإِنْ أَخْطَأَهُ هَذَا نَهَشَهُ هَذَا  

"Increase in remembrance of the severer of pleasures." Meaning death.  

قَالَ رَسُولُ اللَّهِ ﷺ أَكْثِرُوا ذِكْرَ هَاذِمِ اللَّذَّاتِ يَعْنِي الْمَوْتَ قَالَ وَفِي الْبَابِ عَنْ أَبِي سَعِيدٍ  

"When a third of the night had passed, the Messenger of Allah ﷺ stood and said: 'O you people! Remember Allah! Remember Allah! The Rajifah is coming, followed by the Radifah, death and what it brings is coming, death and what it brings is coming!'"

Ubay said that I said, "O Messenger of Allah! I send a lot of Ṣalāt upon you. How much of my Ṣalāt should I make for you?" He said, "As you wish." I said, "˹How about˺ a fourth?" He said, "As you wish, but if do more, it would be better for you." I said, "˹How about˺ one-half?" He said, "As you wish, but if you do more, it would be better for you." I said, "Then ˹how about˺ two-thirds?" He said, "As you wish, but if you do more, it would be better for you."

I said: "Should I make all of my ˹duʿāʾ as˺ Ṣalāt for you?" He said, "˹If you do this˺ it would be sufficient for your concerns and it would be forgiveness for your sins."  

كَانَ رَسُولُ اللَّهِ ﷺ إِذَا ذَهَبَ ثُلُثَا اللَّيْلِ قَامَ فَقَالَ: «يَا أَيُّهَا النَّاسُ، اذْكُرُوا اللَّهَ! اذْكُرُوا اللَّهَ! جَاءَتِ الرَّاجِفَةُ، تَتْبَعُهَا الرَّادِفَةُ، جَاءَ الْمَوْتُ بِمَا فِيهِ! جَاءَ الْمَوْتُ بِمَا فِيهِ!»

قَالَ أُبَىٌّ قُلْتُ: يَا رَسُولَ اللَّهِ، إِنِّي أُكْثِرُ الصَّلاَةَ عَلَيْكَ، فَكَمْ أَجْعَلُ لَكَ مِنْ صَلاَتِي؟ فَقَالَ: «مَا شِئْتَ۔» قَالَ قُلْتُ: الرُّبُعَ؟ قَالَ: «مَا شِئْتَ، فَإِنْ زِدْتَ فَهُوَ خَيْرٌ لَكَ۔» قُلْتُ: النِّصْفَ؟ قَالَ: «مَا شِئْتَ، فَإِنْ زِدْتَ فَهُوَ خَيْرٌ لَكَ۔» قَالَ قُلْتُ: فَالثُّلُثَيْنِ؟ قَالَ: «مَا شِئْتَ، فَإِنْ زِدْتَ فَهُوَ خَيْرٌ لَكَ۔»

قُلْتُ: أَجْعَلُ لَكَ صَلاَتِي كُلَّهَا؟ قَالَ: «إِذًا تُكْفَى هَمَّكَ وَيُغْفَرُ لَكَ ذَنْبُكَ۔»