The single reference in the OT (Jer. 36: 18) probably refers to a mixture of soot and gum arabic which was used for writing on papyrus. Ezekiel (9: 2–3) mentioned an inkhorn which would have contained the ingredients for making ink and could be fastened on to the scribe's belt. Paul (2 Cor. 3: 3) depicts the Corinthian converts as a commendatory letter from Christ, written by Paul, not however with ink but on human hearts.