3 They back returned to the princely place; 4 Where an errant knight in arms clad,

errant > itinerant (a "knight errant" roamed in quest of adventure; the word-order here also implies the sense of erring, deviating, etc.)

5 And heathenish shield, wherein with letters red 6 Was written Sansjoy, they new arrived find:

new > newly

7 Inflamed with fury and fierce hardihood,

hardihood > audacity, boldness; hardness

8 He seemed in heart to harbour thoughts unkind, 9 And nourish bloody vengeance in his bitter mind.

104.39

Who when the shamed shield of slaine Sans foy
2 He spide with that same Faery champions page,
Bewraying him, that did of late destroy
4 His eldest brother, burning all with rage
He to him leapt, and that same enuious gage
6 Of victors glory from him snatcht away:
But th'Elfin knight, which ought that warlike wage,
8 Disdaind to +loose+ the meed he wonne in fray,
And him +rencountring+ fierce, reskewd the noble pray.

8 loose > lose 1609 9 rencountring > re'ncountring 1609