Tolkien wrote at least four versions of the oath itself, as found in The History of Middle-earth. The three earliest versions are found in The Lays of Beleriand: In alliterative verse (circa 1918-1920s), in chapter 2, Poems Early Abandoned. The Flight of the Noldoli from Valinor. Lines 132-141. In rhyming couplets (circa 1928), in chapter 3, The Lay of Leithian. Canto VI, lines 1628-1643. In a different form as restated by Celegorm, third son of Fëanor, in chapter 3, The Lay of Leithian. Canto VI, lines 1848-1857. A later version is found in Morgoth's Ring.