Jeremiah 1:8 - Ellicott's Commentary On The Whole Bible

Be not afraid. — The words imply, as in those spoken to Ezekiel (Ezekiel 2:6), to St. Peter (Luke 5:10), and St. Paul (Acts 18:9), the fear that sprang from the sense of personal weakness and unfitness to cope with the dangers to which his work exposed him. The “faces” of his adversaries would be a source of terror to him. The consciousness that Jehovah was with him was to raise him from that timidity.