Jude 23a is one of the most direct statements on evangelism in the NT: 'snatch others from the fire and save them'. The NRSV has it better in regards to the Greek: 'save others by snatching them out of the fire'. This is the second half of a men-de construct i.e. on the one hand be merciful to those in doubt, and on the other hand, save... The imperative is 'save', the means is 'by snatching them out of the fire'. This is a call to reach out to the lost and save them. Clearly, it in the NT it is God who saves, but he works through believers as his agency, empowered by the Spirit, as they share the Gospel with the lost.
This verse speaks of the dangers of eternal destruction. This is clear from verse 7 where the recipients of the letter are warned of the dangers of 'the punishment of eternal fire'. Sodom and Gomorrah serves as a warning to the readers.
Here we have an appeal from Christ's earthly brother Jude, to be motivated in our evangelism because of the horrendous fate of the lost. The Greek for punishment in Jude 7 is dike which is also used by 2 Thess 1:9 which reads, 'they will be punished with eternal destruction and shut out from the presence of the Lord and from the majesty of his power'. We have here in Jude the same essential theme, eternal punishment in fire. 'Fire' can be literal or figurative. It is difficult to remove the punitive dimension despite many finding this distasteful.
We are then to be motivated to save the lost who will be destroyed in eternal fire. We are to look with compassion and grief upon lost humanity. We are to meditate upon their fate, allowing ourelves to be moved by their fate. We are to care deeply and as Jesus in his mercy has saved us, reach out to save others.
This should move us to action.