Musannaf Ibn Abi Shayba 26:560

Bishr ibn al-Mufaddal narrated to us, from Abd al-Rahman ibn Ishaq, from his father, from Abd al-Rahman ibn Amr ibn Sahl, who said: A freed slave died during the time of Uthman, and he had no patron (mawla). Uthman ordered his wealth, and it was entered into the public treasury (bayt al-mal).