Jerome

Those who are dying shall not live; the giants shall not rise again. Therefore You visited and destroyed them, and wiped out all memory of them. LXX: For the dead shall not see life; nor will physicians bring them back. Therefore You brought in, and destroyed, and took away all their males. Symmachus in a clearer manner: The dead shall not be revived; the giants shall not rise. Therefore You visited and defeated them, and dispersed all memory of them. …

Commentary on Isaiah ↗

Gregory the Dialogist

For hence it is said by the prophet, "The dead shall not live; the giants shall not rise up again." For whom does he call "the dead" except sinners, and whom does he designate "giants" except those who over and above take pride in sin. Now the former do "not live," because by sinning they have forfeited the life of righteousness; these latter too "cannot rise up again" after death because after their transgression they are swollen with pride and do not have recourse to the remedies of penitence.

Morals on the Book of Job, Book 17, Section 30 ↗

Thomas Aquinas

614. Let not the dead live. Here the prophet asks that God not free those punished from further punishment. And first, he sets out the petition: let not the dead, sinners, live, in the life of glory, unless they repent; let not the giants, glorying in their own power, rise again, to glory: the wicked shall not rise again in judgment (Ps 1:5); the ancient giants did not obtain pardon for their sins (Sir 16:8); or he asks that their fallen enemies not rise again further to power. …

Commentary on Isaiah ↗