The demons asked Jesus if he had come to torment them before the time because they feared the eternal judgment that awaited them (Revelation 20:10). They tried to ward off Jesus with the words What have you to do with us…?
(also in Mark 1:24). They reminded Jesus, with even an oath invoking God’s name (Mark 5:7) that their time of torment had not yet arrived.
The torment these demons refer to is the eternal judgment that awaits them (see Revelation 20:10). Despite being already aware of their inevitable defeat, these demons still tried to resist Jesus. Here we see them trying to save what they can. They try to ward off Jesus with the words what have you to do with us?
(see also Mark 1:24). They appeal to him as the Son of God, even reminding him (in the name of God: Mark 5:7) that their time of torment had not yet arrived.1
29 And behold, they cried out, “What have you to do with us, O Son of God? Have you come here to torment us before the time?”