Musnad Abu Ya'la al-Mawsili 3:283

Abu Musa narrated to us, Abu Ahmad narrated to us, Sufyan narrated to us, from Abu Ishaq, from Abu al-Khalil, from Ali, who said: Al-Mughirah ibn Shu'bah had a spear. Whenever we went out with the Messenger of Allah (may Allah bless him and grant him peace) on a military expedition, he would plant it in the ground, and people would pass by it and carry it. I said to him, "If I come to the Prophet (may Allah bless him and grant him peace), I will certainly inform him." He said, "If you do that, you will not return a lost item."