إن الناس قد أنكروا منك أنك تخرج في البرد في الملاءتين، وتخرج في الحر في الحشو والثوب الغليظ! قال: أو لم تكن معنا بخيبر؟ قال: بلى. قال: فإن رسول الله بعث أبا بكر، وعقد له لواء، فرجع، وبعث عمر، وعقد له لواء، فرجع بالناس. فقال رسول الله: لأعطين الراية رجلا يحب الله ورسوله، ويحبه الله ورسوله، ليس بفرار. فأرسل إلي وأنا أرمد، قلت: إني أرمد فتفل في عيني، وقال: اللهم اكفه أذى الحر والبرد. فما وجدت حرا بعد ذلك ولا بردا.
[‘Ali was told,] The people disapprove of you going out in the cold wearing thin sheets of clothing, and going out in the heat wearing thick and coarse clothing! He said, “Were you not with us in Khaybar?” He said, “But of course.” He said, “The Messenger of Allah salla Llahu ‘alayhi wa sallam dispatched Abu Bakr and gave him the standard to carry. (But) he returned, unsuccessful. Then he dispatched ‘Umar and gave him the standard to carry. (But) he (too) returned to the people, unsuccessful. The Messenger of Allah salla Llahu ‘alayhi wa sallam then said, “I will most certainly give this standard to a man who loves Allah and His Messenger; and Allah and His Messenger love him. He does not flee (the battle field).” Nabi salla Llahu ‘alayhi wa sallam called for me and I was, at that time, suffering from inflammation of the eyes. I said to him, “I am suffering from inflammation of the eyes.” So he applied his saliva in my eyes and said, “O Allah, be sufficient for him in the heat and the cold.” After that, I did not experience (too much) heat or (too much) cold.”
This hadith is narrated from ‘Ali.
Imam al Nasa’i and others narrate from Ibn Abi Layla — from al Hakam and al Minhal — from ‘Abdul Rahman ibn Abi Layla — from his father — who said to ‘Ali (the above). His father used to travel with ‘Ali.
Ibn Abi Layla’s name is Muhammad ibn ‘Abdul Rahman. He is da’if (weak). Al Hakam’s name is ibn ‘Utaybah. Al Minhal’s name is ibn ‘Amr.
Imam al Nasa’i narrates with a da’if (weak) chain of transmission. It contains Abu Ishaq al Sabi’i. He is a mudallis (obfuscates when he transmits) and a mukhtalit (commits serious errors). Ayub ibn Ibrahim was only deemed a thiqah (reliable) by Ibn Hibban.
 Imam al Nasa’i: al Sunan al Kubra, hadith no. 8345 and al Khasa’is ‘Ali, hadith no. 14.
 Imam al Nasa’i: al Sunan al Kubra, hadith no. 8483.