What do people fear in Jude 1:23? I know fear can mean multiple things. But what I'm getting out of Jude 1:23 is that people saved others by fearing something. Do they fear Satan? Or do they fear God? The whole time, I was assuming fear was a bad thing.

120 But ye, beloved, building up yourselves on your most holy faith, praying in the Holy Ghost, 21 keep yourselves in the love of God, looking for the mercy of our Lord Jesus Christ unto eternal life. 22 And of some have compassion, making a difference: 23 and others save with fear, pulling them out of the fire; hating even the garment spotted by the flesh.
[KJV] my emphasis
I think Jude is encouraging his readers to fear the temptation of the flesh, which explains the following statement "hating even the garment spotted by the flesh.". Look at how it's phrased in the New Living Translation:


  Jude 1:20-23 NLT But you, dear friends, must build each other up in your most holy faith, pray in the power of the Holy Spirit, and await the mercy of our Lord Jesus Christ, who will bring you eternal life. In this way, you will keep yourselves safe in God’s love. And you must show mercy to those whose faith is wavering. Rescue others by snatching them from the flames of judgment. Show mercy to still others, but do so with great caution, hating the sins that contaminate their lives.


Instead of the fear, it's saying the word caution. This is similar to the passage in Galatians 6:


  Galatians 6:1 NLT Dear brothers and sisters, if another believer is overcome by some sin, you who are godly should gently and humbly help that person back onto the right path. And be careful not to fall into the same temptation yourself.


It looks like it is a cautionary fear.