Mustadrak al-Hakim — Hadith 2465

It is narrated from Aslam Abu Imran that we set out from Madinah on a military expedition towards Constantinople. The commander of the army was Sayyiduna Abd al-Rahman bin Khalid bin al-Walid (may Allah be pleased with him), and the Romans had their backs against the wall of the city. Suddenly a man, all alone, charged at the enemy army, and the people cried out: Stop, stop! La ilaha illallah (there is no god but Allah)! This man is throwing himself into destruction with his own hands. Then Sayyiduna Abu Ayyub al-Ansari (may Allah be pleased with him) said: O people, this verse was revealed about us, the Ansar. When Allah helped His Prophet and made Islam prevail, we said (among ourselves): Come, let us now stay with our property and tend to it. Then Allah, the Mighty and Majestic, revealed this verse: "And spend in the way of Allah and do not throw yourselves into destruction with your own hands" [Surah al-Baqarah: 195]. So throwing oneself into destruction with one's own hands is in fact that we become absorbed in tending our property, sit back, and abandon jihad. Abu Imran said: Sayyiduna Abu Ayyub (may Allah be pleased with him) continued to wage jihad in the way of Allah until he was buried in Constantinople itself.
This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it.