Musannaf Ibn Abi Shayba 33:877

Waki’ narrated to us, from Talha bin Yahya, that Umar bin Abdul Aziz used to use the postal service (barid). He said: A freed slave of his carried a man on the postal service without his permission. He said: So he summoned him and said, "Do not leave until you appraise it, then place its value into the public treasury (Bayt al-Mal)."