It is narrated from Sayyiduna Abdullah bin Abi Awfa (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "Do not wish to meet the enemy; rather, ask Allah for well-being. But when you do meet the enemy, be steadfast, and know that Paradise is beneath the shade of swords."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السير / 18078