Faith is a journey. It has a beginning and an end. Faith starts by God revealing it to us. Before this faith came, we were held prisoners by the law, locked up until faith should be revealed. (Galatians 3:23). Listening to, and obeying Jesus, is Jesus being the author and finisher [perfecter] of our faith, Heb 12:2. Jesus authors our faith by laying the foundation of our faith on rock.
Whoever comes to me, and listens to my words and does [practices, obeys] them, I will show you what he is like. He is like a man who built a house, and dug deep and laid the foundation securely built on a rock; and when the flood arose, the torrent beat violently upon that house, but could not shake it because it was founded on a rock. Luke 6:47-48.
And when we hear His words , the foundation of our faith has been set in rock, a rock so solid that the gates of Hell cannot prevail against it. Jesus finishes our faith when we see Him bring our salvation: He will appear the second time, not to bear sin, but to bring full salvation to those who are waiting for and expecting him. Heb 9:28. For the grace of God that brings salvation …Tit 2:11; looking for the mercy of our Lord Jesus Christ to bring eternal life. Jude 1:21; Receiving the end of your faith – the salvation of your souls. 1 Pet 1:9
We are saved through faith, and by faith our hearts are purified; but obviously in the beginning of faith, we are not purified, neither are we saved. We must contend for the faith, grow in the faith, build up our faith, increase in faith, perfect what is lacking in our faith, fight the good fight of faith, until victory, when our faith is finished by the finisher; faith is a process and a journey, the end of which is to see Christ bring our salvation, to bring our eternal life.