Allah said,[يَـأَيُّهَا النَّبِىُّ حَرِّضِ الْمُؤْمِنِينَ عَلَى الْقِتَالِ]
(O Prophet! Urge the believers to fight), encouraged and called them to fight. The Messenger of Allah used to encourage the Companions to fight when they faced the enemy.
On the day of Badr when the idolators came with their forces and supplies, he said to his Companions,
«قُومُوا إِلَى جَنَّةٍ عَرْضُهَا السَّمَوَاتُ وَالْأَرْض»
(Get ready and march forth towards a Paradise as wide as the heavens and earth.)
`Umayr bin Al-Humam said, "As wide as the heavens and earth'' The Messenger said,
«نَعَم»
(Yes) `Umayr said, "Excellent! Excellent!'' The Messenger asked him,
«مَا يَحْمِلُكَ عَلَى قَوْلِكَ: بَخٍ بَخ»
(What makes you say, `Excellent! Excellent!') He said, "The hope that I might be one of its dwellers.'' The Prophet said,
«فَإِنَّكَ مِنْ أَهْلِهَا»
(You are one of its people.) Umayr went ahead, broke the scabbard of his sword, took some dates and started eating from them. He then threw the dates from his hand, saying, "Verily, if I lived until I finished eating these dates, then it is indeed a long life.'' He went ahead, fought and was killed, may Allah be pleased with him.
Surah Anfal - tafsir ibn Kathir;
PDF