infirmity > weakness; hence: fatigue; also, in tune with the allegory: weakness of character, moral frailty
5 Greatly he grew enraged, and furiously 6 Hurling his sword away, he lightly leapt
lightly > quickly
7 Upon the beast, that with great cruelty 8 Roared, and raged to be under-kept: 9 Yet he perforce him held, and strokes upon him heaped.
perforce > by force
307.34
As he that striues to stop a suddein flood,
2 And in strong banckes his violence +enclose+,
Forceth it swell aboue his wonted mood,
4 And largely ouerflow the fruitfull plaine,
That all the countrey seemes to be a Maine,
6 And the rich furrowes flote, all quite fordonne:
The wofull husbandman doth lowd complaine,
8 To see his whole yeares labour lost so soone,
For which to God he made so many an idle boone.
2 enclose > containe sugg. various editors
1 As he that strives to stop a sudden flood, 2 And in strong banks its violence enclose,
enclose > [does] contain, [to] contain