From his father who said: "When the Messenger of Allah ﷺ sent a commander of an army, he would exhort him concerning himself to have Taqwa of Allah, and he would exhort him to be good to those who are with him among the Muslims. He would say: 'Fight in the Name of Allah, in the cause of Allah. Fight those who disbelieve in Allah, and do not steal from the spoils of war or be treacherous, nor mutilate, and do not kill a child. When you meet your enemy among the idolaters, then call them to one of the three options or choices, whichever of them they respond to then accept it from them, and refrain from them. Call them to Islam, and to relocate from their land to the land of Emigrants. Inform them that if they do that, then they will have similar to what those who emigrated have, and from them will be required similar to what is required from those who have emigrated. And if they refuse to relocate, then inform them that they will be like the Bedouins among the Muslim, and they will be treated the same as Bedouins are treated. There is no war spoils or Fay' for them, unless they fight along with the Muslims. If they refuse then seek aid from Allah against them and fight them. And if you lay siege to a fortress and they want you to grant them covenant from Allah and a covenant of His Prophet, then do not grant them the covenant of Allah nor the covenant of His Prophet. Rather grant them your own covenant and the covenant of your companions, it will be better than breaking Allah's covenant and the covenant of His Messenger. And if you lay siege to the people of a fortress and they want you to lift the siege for negotiating upon the judgement of Allah, then do not stop, but rather make them surrender to your judgement, for you do not know if you will come upon the judgement of Allah regarding them or not.' Or similar to that."  

كَانَ رَسُولُ اللَّهِ ﷺ إِذَا بَعَثَ أَمِيرًا عَلَى جَيْشٍ أَوْصَاهُ فِي خَاصَّةِ نَفْسِهِ بِتَقْوَى اللَّهِ وَمَنْ مَعَهُ مِنَ الْمُسْلِمِينَ خَيْرًا وَقَالَ اغْزُوا بِسْمِ اللَّهِ وَفِي سَبِيلِ اللَّهِ قَاتِلُوا مَنْ كَفَرَ بِاللَّهِ وَلاَ تَغُلُّوا وَلاَ تَغْدِرُوا وَلاَ تُمَثِّلُوا وَلاَ تَقْتُلُوا وَلِيدًا فَإِذَا لَقِيتَ عَدُوَّكَ مِنَ الْمُشْرِكِينَ فَادْعُهُمْ إِلَى إِحْدَى ثَلاَثِ خِصَالٍ أَوْ خِلاَلٍ أَيَّتَهَا أَجَابُوكَ فَاقْبَلْ مِنْهُمْ وَكُفَّ عَنْهُمُ ادْعُهُمْ إِلَى الإِسْلاَمِ وَالتَّحَوُّلِ مِنْ دَارِهِمْ إِلَى دَارِ الْمُهَاجِرِينَ وَأَخْبِرْهُمْ إِنْ فَعَلُوا ذَلِكَ فَإِنَّ لَهُمْ مَا لِلْمُهَاجِرِينَ وَعَلَيْهِمْ مَا عَلَى الْمُهَاجِرِينَ وَإِنْ أَبَوْا أَنْ يَتَحَوَّلُوا فَأَخْبِرْهُمْ أَنَّهُمْ يَكُونُوا كَأَعْرَابِ الْمُسْلِمِينَ يَجْرِي عَلَيْهِمْ مَا يَجْرِي عَلَى الأَعْرَابِ لَيْسَ لَهُمْ فِي الْغَنِيمَةِ وَالْفَىْءِ شَيْءٌ إِلاَّ أَنْ يُجَاهِدُوا فَإِنْ أَبَوْا فَاسْتَعِنْ بِاللَّهِ عَلَيْهِمْ وَقَاتِلْهُمْ وَإِذَا حَاصَرْتَ حِصْنًا فَأَرَادُوكَ أَنْ تَجْعَلَ لَهُمْ ذِمَّةَ اللَّهِ وَذِمَّةَ نَبِيِّهِ فَلاَ تَجْعَلْ لَهُمْ ذِمَّةَ اللَّهِ وَلاَ ذِمَّةَ نَبِيِّهِ وَاجْعَلْ لَهُمْ ذِمَّتَكَ وَذِمَمَ أَصْحَابِكَ لأَنَّكُمْ إِنْ تُخْفِرُوا ذِمَّتَكُمْ وَذِمَمَ أَصْحَابِكُمْ خَيْرٌ مِنْ أَنْ تُخْفِرُوا ذِمَّةَ اللَّهِ وَذِمَّةَ رَسُولِهِ وَإِذَا حَاصَرْتَ أَهْلَ حِصْنٍ فَأَرَادُوكَ أَنْ تُنْزِلَهُمْ عَلَى حُكْمِ اللَّهِ فَلاَ تُنْزِلُوهُمْ وَلَكِنْ أَنْزِلْهُمْ عَلَى حُكْمِكَ فَإِنَّكَ لاَ تَدْرِي أَتُصِيبُ حُكْمَ اللَّهِ فِيهِمْ أَمْ لاَ أَوْ نَحْوَ هَذَا  

"Abu Ahmad narrated to us from Sufyan (who said): "Alqamah bin Marthad narrated to us' - and it is similar in its meaning, but he added in it: "if they refuse, then take the Jizyah from them, and it they refuse then seek aid from Allah against them."  

That the Prophet ﷺ would not attack except near the time of Fajr, so if he heard the Adhan he would refrain, and if not, then he would attack. So he listened one day and heard a man saying: "Allahu Akbar, Allahu Akbar," so he said: "Upon the Fitrah." Then he said: "I bear witness that none has the right to be worshipped but Allah." So he said: "You have departed from the Fire."  

كَانَ النَّبِيُّ ﷺ لاَ يُغِيرُ إِلاَّ عِنْدَ صَلاَةِ الْفَجْرِ فَإِنْ سَمِعَ أَذَانًا أَمْسَكَ وَإِلاَّ أَغَارَ فَاسْتَمَعَ ذَاتَ يَوْمٍ فَسَمِعَ رَجُلاً يَقُولُ اللَّهُ أَكْبَرُ اللَّهُ أَكْبَرُ فَقَالَ عَلَى الْفِطْرَةِ فَقَالَ أَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ فَقَالَ خَرَجْتَ مِنَ النَّارِ  

] This Hadith is Hasan Sahih.