1644, Samuel Rutherford, Lex Rex, or The Law and the Prince, 1846, The Presbyterian's Armoury, Volume 3, 211, But why are not the kings, even Nero, Julian, Nebuchadnezzar, and Belshazzar, vicegerents of Christ, as mediator, as priest, as redeemer, as prophet, as advocate, presenting our prayers to God his father?
Source: wiktionary