3 His pace he freshly forward did advance, 4 And carried her beyond all jeopardy; 5 But naught that wants rest can long aby.
aby > abide, endure, remain
6 He, having through incessant travel spent
travel > travel; travail
7 His force, at last perforce adown did lie,
adown > down
8 Nor foot could further move: the lady gent
gent > noble, high-born; graceful, elegant
9 Thereat was sudden struck with great astonishment,
Thereat > As a result of that astonishment > dismay; bewilderment