عَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَ لَا تَمَنَّوْا لِقَاءَ الْعَدُوِّ فَإِذَا لَقِيتُمُوهُ فَاصْبِرُوا وَفِي لَفْظٍ فَإِنَّكُمْ لَا تَدْرُونَ مَا يَكُونُ فِي ذَلِكَ
It is narrated from Sayyiduna Abu Hurairah, may Allah be pleased with him, that the Noble Prophet, peace and blessings be upon him, said: Do not wish to meet the enemies, but when you encounter them, be patient. In another narration it is stated: Because you do not know what will happen in that battle (therefore do not wish for it).