Musnad Ahmad 778
It was narrated that ‘Abdur-Rahman bin Abi Laila said:
My father used to chat at night with `Ali, and ‘Ali used to wear summer clothes in the winter and winter clothes in the summer. It was said to him: Why don`t you ask him [about that]? He asked him and he said: The Messenger of Allah (ﷺ) sent for me when I had a sore eye on the day of Khaibar. I said: O Messenger of Allah, my eye is sore. He spat in my eye and said: `O Allah, take away heat and cold from him.” And I have never felt any heat or cold since that day. And he [the Prophet      (ﷺ)] said: `I shall certainly give the banner to a man who loves Allah and his Messenger, and Allah and His Messenger love him, and he is not one to runaway.` The Companions of the Prophet (ﷺ)  hoped for it, but he gave it to me.
حَدَّثَنَا وَكِيعٌ، عَنْ ابْنِ أَبِي لَيْلَى، عَنِ الْمِنْهَالِ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ أَبِي لَيْلَى، قَالَ كَانَ أَبِي يَسْمُرُ مَعَ عَلِيٍّ وَكَانَ عَلِيٌّ يَلْبَسُ ثِيَابَ الصَّيْفِ فِي الشِّتَاءِ وَثِيَابَ الشِّتَاءِ فِي الصَّيْفِ فَقِيلَ لَهُ لَوْ سَأَلْتَهُ فَسَأَلَهُ فَقَالَ إِنَّ رَسُولَ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ بَعَثَ إِلَيَّ وَأَنَا أَرْمَدُ الْعَيْنِ يَوْمَ خَيْبَرَ فَقُلْتُ يَا رَسُولَ اللَّهِ إِنِّي أَرْمَدُ الْعَيْنِ قَالَ فَتَفَلَ فِي عَيْنِي وَقَالَ اللَّهُمَّ أَذْهِبْ عَنْهُ الْحَرَّ وَالْبَرْدَ فَمَا وَجَدْتُ حَرًّا وَلَا بَرْدًا مُنْذُ يَوْمِئِذٍ وَقَالَ لَأُعْطِيَنَّ الرَّايَةَ رَجُلًا يُحِبُّ اللَّهَ وَرَسُولَهُ وَيُحِبُّهُ اللَّهُ وَرَسُولُهُ لَيْسَ بِفَرَّارٍ فَتَشَرَّفَ لَهَا أَصْحَابُ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَأَعْطَانِيهَا‏.‏