When reading scripture, it is important to look both back and forward from a particular verse to get some context:
17 But you must remember, beloved, the predictions of the apostles of our Lord Jesus Christ;
18 they said to you, “In the last time there will be scoffers, following their own ungodly passions.”
19 It is these who set up divisions, worldly people, devoid of the Spirit.
20 But you, beloved, build yourselves up on your most holy faith; pray in the Holy Spirit;
21 keep yourselves in the love of God; wait for the mercy of our Lord Jesus Christ unto eternal life.
22 And convince some, who doubt;
23 save some, by snatching them out of the fire; on some have mercy with fear, hating even the garment spotted by the flesh.
So the audience here is Christ’s beloved, which are His followers: the Church.
The advice being given is, to pray in the Holy Spirit to build yourself up on the foundation that is our faith and to remain in the love of God, especially in the midst of the end times and when among those who reject God and His will.
When we turn to the Holy Spirit in prayer and allow Him to set our hearts ablaze and to work through us, we become powerful instruments in the hands of God. Through the gifts and fruits of the Holy Spirit, we become both firmer in our faith, and a brighter shining examples to others.
We can save no one else from the fires on our own, but by grace and the power of the Holy Spirit, others may be convinced, saved, and snatched out of the fire.
So to answer the question of who does this, I would say that we, the faithful do.
Come Holy Spirit,
fill the hearts of your faithful
and kindle in them the fire of your love.
Send forth your Spirit and they shall be created.
And You shall renew the face of the earth.
O, God,
who by the light of the Holy Spirit,
did instruct the hearts of the faithful,
grant that by the same Holy Spirit
we may be truly wise and ever rejoice in His consolations,
Through Christ Our Lord, Amen.
