Musannaf Ibn Abi Shayba 28:484

Waki’ narrated to us, he said: Sufyan narrated to us, from Abu Ishaq, from Abu al-Khalil, from Ali, who said: When al-Mughira ibn Shu’bah would go on a military expedition with the Prophet, may Allah bless him and grant him peace, he would carry a spear with him. When he returned, he would cast it aside so that it would be carried for him. So Ali said to him, "I will certainly mention this to the Prophet, may Allah bless him and grant him peace." He said, "Do not do it, for if you do, you will not raise a lost item."