Musnad Ahmad 802
It was narrated that Fadalah bin Abi Fadalah al-Ansari - and Abu Fadalah was one of the people of Badr-said:
I went out with my father to visit `Ali bin Abi Talib (رضي الله عنه) when he was sick and had become very ill. My father said to him: What is keeping you here? If you die, there will be no one to take care of your (burial) except the Bedouin of Juhainah. It is better for you to be carried to Madinah, then if you die your companions will take care of you and offer the funeral prayer for you, ‘Ali                    (رضي الله عنه) said: The Messenger of Allah (ﷺ) promised me that I would not die until I am appointed leader, then this - meaning his beard - will be dyed from the blood of this - meaning his head, Then he was killed, and Abu Fadalah was killed fighting alongside ‘Ali on the day of Siffeen.
حَدَّثَنَا هَاشِمُ بْنُ الْقَاسِمِ، حَدَّثَنَا مُحَمَّدٌ يَعْنِي ابْنَ رَاشِدٍ، عَنْ عَبْدِ اللَّهِ بْنِ مُحَمَّدِ بْنِ عَقِيلٍ، عَنْ فَضَالَةَ بْنِ أَبِي فَضَالَةَ الْأَنْصَارِيِّ، وَكَانَ أَبُو فَضَالَةَ، مِنْ أَهْلِ بَدْرٍ قَالَ خَرَجْتُ مَعَ أَبِي عَائِدًا لِعَلِيِّ بْنِ أَبِي طَالِبٍ رَضِيَ اللَّهُ عَنْهُ مِنْ مَرَضٍ أَصَابَهُ ثَقُلَ مِنْهُ قَالَ فَقَالَ لَهُ أَبِي مَا يُقِيمُكَ فِي مَنْزِلِكَ هَذَا لَوْ أَصَابَكَ أَجَلُكَ لَمْ يَلِكَ إِلَّا أَعْرَابُ جُهَيْنَةَ تُحْمَلُ إِلَى الْمَدِينَةِ فَإِنْ أَصَابَكَ أَجَلُكَ وَلِيَكَ أَصْحَابُكَ وَصَلَّوْا عَلَيْكَ فَقَالَ عَلِيٌّ رَضِيَ اللَّهُ عَنْهُ إِنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ عَهِدَ إِلَيَّ أَنْ لَا أَمُوتَ حَتَّى أُؤَمَّرَ ثُمَّ تُخْضَبَ هَذِهِ يَعْنِي لِحْيَتَهُ مِنْ دَمِ هَذِهِ يَعْنِي هَامَتَهُ فَقُتِلَ وَقُتِلَ أَبُو فَضَالَةَ مَعَ عَلِيٍّ يَوْمَ صِفِّينَ‏.‏