Musnad Ahmad 2:63

Abu Sa’id narrated to us, ‘Abd al-‘Aziz ibn Muhammad narrated to us, Salih ibn Muhammad ibn Za’idah narrated to us, from Salim ibn ‘Abd Allah, that he was with Maslamah ibn ‘Abd al-Malik in the land of the Byzantines. He found spoils of war (ghulul) in a man’s belongings, so he asked Salim ibn ‘Abd Allah. He said: ‘Abd Allah narrated to me, from ‘Umar, that the Messenger of Allah (peace and blessings of Allah be upon him) said: “Whoever you find in his belongings spoils of war, then burn them.” He said: And I think he said: “And beat him.” He said: So he brought out his belongings in the marketplace. He said: He found a Mushaf (copy of the Quran) among them, so he asked Salim, and he said: “Sell it, and give its price in charity.”