3 And from his wide devouring oven sent 4 A flake of fire that, flashing in his beard,
flake > {Flash; fragment of burning matter} his > [the knight's]
5 Him all amazed, and almost made afeard:
amazed > confused, confounded; overwhelmed almost > for the most part afeard > frightened
6 The scorching flame sore swinged all his face,
swinged > singed
7 And through his armour all his body seared, 8 That he could not endure so cruel case,
That > [So that] case > [a] plight; also, punningly: case, enclosure
9 But thought his arms to leave, and helmet to unlace.
arms > {Weapons, shield and armour}