Command to not wish to meet the enemy and to show patience when you face them; Duʿāʾ when meeting the enemy

(the freed slave of 'Umar bin 'Ubaidullah) I was Umar's clerk. Once Abdullah bin Abi Aufa wrote a letter to 'Umar when he proceeded to Al-Haruriya. I read in it that Messenger of Allah ﷺ in one of his military expeditions against the enemy, waited till the sun declined and then he got up amongst the people saying, "O people! Do not wish to meet the enemy, and ask Allah for safety, but when you face the enemy, be patient, and remember that Paradise is under the shades of swords." Then he said, "O Allah, the Revealer of the Holy Book, and the Mover of the clouds and the Defeater of the clans, defeat them, and grant us victory over them."  

حِينَ خَرَجَ إِلَى الْحَرُورِيَّةِ فَقَرَأْتُهُ فَإِذَا فِيهِ إِنَّ رَسُولَ اللَّهِ ﷺ فِي بَعْضِ أَيَّامِهِ الَّتِي لَقِيَ فِيهَا الْعَدُوَّ انْتَظَرَ حَتَّى مَالَتِ الشَّمْسُ ثُمَّ قَامَ فِي النَّاسِ فَقَالَ: «أَيُّهَا النَّاسُ، لاَ تَمَنَّوْا لِقَاءَ الْعَدُوِّ، وَسَلُوا اللَّهَ الْعَافِيَةَ۔ فَإِذَا لَقِيتُمُوهُمْ، فَاصْبِرُوا وَاعْلَمُوا أَنَّ الْجَنَّةَ تَحْتَ ظِلاَلِ السُّيُوفِ۔» ثُمَّ قَالَ: «(اللَّهُمَّ مُنْزِلَ الْكِتَابِ، وَمُجْرِيَ السَّحَابِ، وَهَازِمَ الأَحْزَابِ، اهْزِمْهُمْ وَانْصُرْنَا عَلَيْهِمْ)۔»  

The Prophet ﷺ said: "Do not wish to meet the enemy, but when you meet face) the enemy, be patient."  

عَنِ النَّبِيِّ ﷺ قَالَ لاَ تَمَنَّوْا لِقَاءَ الْعَدُوِّ فَإِذَا لَقِيتُمُوهُمْ فَاصْبِرُوا