Hadith: Whoever kills someone in battle, having a proof for that, his belongings are his.

عن أبي قتادة الأنصاري رضي الله عنه قال: «خَرَجْنَا مَعَ رَسُول الله صلى الله عليه وسلم إلَى حُنَيْنٍ -وَذَكَرَ قِصَّةً- فَقَالَ رَسُولُ الله صلى الله عليه وسلم : مَنْ قَتَلَ قَتِيلاً لَهُ عَلَيْهِ بَيِّنَةٌ فَلَهُ سَلَبُهُ» قَالَهَا ثَلاثاً.
[صحيح] - [متفق عليه]

Abu Qatādah al-Ansāri (may Allah be pleased with him) reported: We went out with the Prophet (may Allah's peace and blessings be upon him) to Hunayn. He narrated a story. Then, the Prophet (may Allah's peace and blessings be upon him) said: "Whoever kills someone in battle, having a proof for that, his belongings are his." He said it three times.
[Authentic hadith] - [Narrated by Bukhari & Muslim]

Explanation

The Prophet (may Allah's peace and blessings be upon him) said on the Day of Hunayn: "Whoever kills someone in battle, having a proof for that, his belongings are his." The proof refers to the clothing, weapons, or the riding animal of the killed person. During that battle, Abu Qatādah killed someone and said to the people around him: "I killed someone." And he implored, by Allah, the ones who witnessed it to testify about it. He said this three times.