Messenger of Allah ﷺ set out for Tabuk. appointing ʿAli as his deputy (in Medina). ʿAli said, "Do you want to leave me with the children and women?" The Prophet ﷺ said, "Will you not be pleased that you will be to me like Aaron to Moses? But there will be no prophet after me."  

أَنَّ رَسُولَ اللَّهِ ﷺ خَرَجَ إِلَى تَبُوكَ وَاسْتَخْلَفَ عَلِيًّا فَقَالَ أَتُخَلِّفُنِي فِي الصِّبْيَانِ وَالنِّسَاءِ قَالَ أَلاَ تَرْضَى أَنْ تَكُونَ مِنِّي بِمَنْزِلَةِ هَارُونَ مِنْ مُوسَى إِلاَّ أَنَّهُ لَيْسَ نَبِيٌّ بَعْدِي وَقَالَ أَبُو دَاوُدَ حَدَّثَنَا شُعْبَةُ عَنِ الْحَكَمِ سَمِعْتُ مُصْعَبًا  

That he heard the Prophet ﷺ on the day (of the battle) of Khaibar saying, "I will give the flag to a person at whose hands Allah will grant victory." So, the companions of the Prophet ﷺ got up, wishing eagerly to see to whom the flag will be given, and everyone of them wished to be given the flag. But the Prophet asked for ʿAli. Someone informed him that he was suffering from eye-trouble. So, he ordered them to bring ʿAli in front of him. Then the Prophet ﷺ spat in his eyes and his eyes were cured immediately as if he had never any eye-trouble. ʿAli said, "We will fight with them (i.e. infidels) till they become like us (i.e. Muslims)." The Prophet ﷺ said, "Be patient, till you face them and invite them to Islam and inform them of what Allah has enjoined upon them. By Allah! If a single person embraces Islam at your hands (i.e. through you), that will be better for you than the red camels."  

اللَّهِ بْنُ مَسْلَمَةَ الْقَعْنَبِيُّ حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ أَبِي حَازِمٍ عَنْ أَبِيهِ عَنْ سَهْلِ بْنِ سَعْد ٍ ؓ سَمِعَ النَّبِيَّ ﷺ يَقُولُ يَوْمَ خَيْبَرَ لأُعْطِيَنَّ الرَّايَةَ رَجُلاً يَفْتَحُ اللَّهُ عَلَى يَدَيْهِ فَقَامُوا يَرْجُونَ لِذَلِكَ أَيُّهُمْ يُعْطَى فَغَدَوْا وَكُلُّهُمْ يَرْجُو أَنْ يُعْطَى فَقَالَ أَيْنَ عَلِيٌّ فَقِيلَ يَشْتَكِي عَيْنَيْهِ فَأَمَرَ فَدُعِيَ لَهُ فَبَصَقَ فِي عَيْنَيْهِ فَبَرَأَ مَكَانَهُ حَتَّى كَأَنَّهُ لَمْ يَكُنْ بِهِ شَىْءٌ فَقَالَ نُقَاتِلُهُمْ حَتَّى يَكُونُوا مِثْلَنَا فَقَالَ عَلَى رِسْلِكَ حَتَّى تَنْزِلَ بِسَاحَتِهِمْ ثُمَّ ادْعُهُمْ إِلَى الإِسْلاَمِ وَأَخْبِرْهُمْ بِمَا يَجِبُ عَلَيْهِمْ فَوَاللَّهِ لأَنْ يُهْدَى بِكَ رَجُلٌ وَاحِدٌ خَيْرٌ لَكَ مِنْ حُمْرِ النَّعَمِ  

Ali remained behind the Prophet ﷺ during the battle of Khaibar as he way suffering from some eye trouble but then he said, "How should I stay behind Messenger of Allah ﷺ?" So, he set out till he joined the Prophet. On the eve of the day of the conquest of Khaibar, Messenger of Allah ﷺ said, "(No doubt) I will give the flag or, tomorrow, a man whom Allah and His Apostle love or who loves Allah and His apostle will take the flag. Allah will bestow victory upon him." Suddenly 'Ali joined us though we were not expecting him. The people said, "Here is 'Ali. "So, Messenger of Allah ﷺ gave the flag to him and Allah bestowed victory upon him.  

كَانَ عَلِيٌّ ؓ تَخَلَّفَ عَنِ النَّبِيِّ ﷺ فِي خَيْبَرَ وَكَانَ بِهِ رَمَدٌ فَقَالَ أَنَا أَتَخَلَّفُ عَنْ رَسُولِ اللَّهِ ﷺ فَخَرَجَ عَلِيٌّ فَلَحِقَ بِالنَّبِيِّ ﷺ فَلَمَّا كَانَ مَسَاءُ اللَّيْلَةِ الَّتِي فَتَحَهَا فِي صَبَاحِهَا فَقَالَ رَسُولُ اللَّهِ ﷺ لأُعْطِيَنَّ الرَّايَةَ أَوْ قَالَ لَيَأْخُذَنَّ غَدًا رَجُلٌ يُحِبُّهُ اللَّهُ وَرَسُولُهُ أَوْ قَالَ يُحِبُّ اللَّهَ وَرَسُولَهُ يَفْتَحُ اللَّهُ عَلَيْهِ فَإِذَا نَحْنُ بِعَلِيٍّ وَمَا نَرْجُوهُ فَقَالُوا هَذَا عَلِيٌّ فَأَعْطَاهُ رَسُولُ اللَّهِ ﷺ فَفَتَحَ اللَّهُ عَلَيْهِ