Let Thine Lover Go

Do tell me, who was it; please tell me who! Whoever said, "Should thou love another, And shown a chance to prove thine love is true: Should thine lover find another lover, Let thy lover be free from any chains, And thou art true love—away let it fly, Let thy beloved be unbound by reigns, Unprotestingly. Thou art should not cry." Sayeth they, "True, noble love we define, And confirm, only if thou art, free be. Love only can be fine as aged wine, If when needed, thy lovers are set free." Yet even when I know this is so, I simply can't let thine true lover go.