Musannaf Ibn Abi Shayba 13:637

Abu Bakr narrated to us, he said: Jarir narrated to us, from Mughira, who said: Al-Hajjaj used to give the people their provisions (rizq). He would say to the recipients of the provisions: "Whoever wishes may take four jaribs of barley for two jaribs of wheat from what belongs to him." So they asked Ibrahim and Al-Sha'bi, and they both said: "There is no harm in it."