I shall certainly give this standard in the hand of one who loves Allah and his Messenger and Allah will grant victory at his hand. Umar b. Khattab said: Never did I cherish for leadership but on that day. I came before him with the hope that I may be called for this, but Messenger of Allah ﷺ called 'Ali b. Abu Talib and he conferred (this honour) upon him and said: Proceed on and do not look about until Allah grants you victory, and 'Ali went a bit and then halted and did not look about and then said in a loud voice: Messenger of Allah, on what issue should I fight with the people? Thereupon he (the Prophet) said: Fight with them until they bear testimony to the fact that there is no god but Allah and Muhammad is his Messenger, and when they do that then their blood and their riches are inviolable from your hands but what is justified by law and their reckoning is with Allah. (Using translation from Muslim 2405)   

أَنَّ رَسُولَ اللهِ ﷺ قَالَ يَوْمَ خَيْبَرَ «لَأُعْطِيَنَّ هَذِهِ الرَّايَةَ رَجُلًا يُحِبُّ اللهَ وَرَسُولَهُ يَفْتَحُ اللهُ عَلَيْهِ» قَالَ عُمَرُ بْنُ الْخَطَّابِ مَا أَحْبَبْتُ الْإِمَارَةَ إِلَّا يَوْمَئِذٍ فَدَعَا رَسُولُ اللهِ ﷺ عَلِيَّ بْنَ أَبِي طَالِبٍ فَأَعْطَاهُ إِيَّاهُ وَقَالَ «امْشِ وَلَا تَلْتَفِتْ حَتَّى يَفْتَحَ اللهُ عَلَيْكَ» فَسَارَ عَلِيٌّ شَيْئًا ثُمَّ وَقَفَ وَذَكَرَ قُتَيْبَةُ كَلِمَةً مَعْنَاهَا فَصَرَخَ يَا رَسُولَ اللهِ عَلَى مَاذَا أُقَاتِلُ النَّاسَ؟ قَالَ «قَاتِلْهُمْ حَتَّى يَشْهَدُوا أَنْ لَا إِلَهَ إِلَّا اللهُ وَأَنَّ مُحَمَّدًا رَسُولُ اللهِ فَإِذَا فَعَلُوا ذَلِكَ فَقَدْ عَصَمُوا مِنْكَ دِمَاءَهُمْ وَأَمْوَالَهُمْ إِلَّا بِحَقِّهَا وَحِسَابُهُمْ عَلَى اللهِ»