And fiercely took his trenchant blade in hand,
  With which he stroke so furious and so fell,
  That nothing seemed the puissance could withstand:
  Upon his crest the hardened iron fell,
  But his more hardened crest was armed so well,
  That deeper dint therein it would not make;
  Yet so extremely did the buffet him quell,
  That from thenceforth he shunned the like to take,
But when he saw them come, he did them still forsake.

The knight was wrath to see his stroke beguiled,
  And smote again with more outrageous might;
  But back again the sparkling steel recoiled,
  And left not any mark, where it did light;
  As if in Adamant rock it had been pight.
  The beast impatient of his smarting wound,
  And of so fierce and forcible despite,
  Thought with his wings to stye above the ground;
But his late wounded wing unserviceable found.

Book I, Canto XI