It seems King Ecbert is loosely quoting from the song Turn! Turn! Turn! written by Pete Seeger and made famous by The Byrds when prince Aethelwulf is leaving for battle. But infact he is quoting the Bible - the lines come from the book of Ecclesiastes, as found in the King James version of the Bible.
This episode was together with the next episode 'The Reckoning' leaked by Russian hackers.