2 Leave off their work, unmindful of their smart,

smart > suffering; sorrow; pain

3 To gaze on them; who forth by them do pace, 4 Till they be come to the furthest part: 5 Where was a cave wrought by wondrous art, 6 Deep, dark, uneasy, doleful, comfortless,

uneasy > disagreeable; without ease

7 In which sad Aesculapius, far apart,

Aesculapius > (God of medicine and healing, son of Apollo and
Coronis)

8 Imprisoned was in chains remediless,

remediless > without hope of rescue

9 For that Hippolytus' rent corse he did redress.

For that > Because Hippolytus > (Son of Theseus and Hippolyte (or her sister Antiope): see Met. 15.497 ff., Aen. 7.761 ff., DGDG 10.50) rent corse > torn body redress > restore, revivify