"If of all human sins of deepest dye

  Be fell ingratitude; if doomed to smart

  For this, the fairest angel of the sky

  Was banished into foul and darksome part;

  If mighty sins for mighty vengeance cry,

  Where due atonement cleanses not the heart;

  Beware lest thou beneath such vengeance groan,

  Ingrate! that wouldest not thy sin atone.