Maliks Muwatta Book 36, Hadith Number 51.

Malik related to me that he heard Ibn Shihab say, “The stray camels in the time of Umar ibn al-Khattab were numerous and left alone. No one touched them until the time of Uthman ibn Affan. He ordered that they be publicised and then sold, and if the owner came afterwards, he was given their price.”