Is it possible that we can grow in Holiness, I see scripture that says you can grow in Grace 2 Peter 3:18, I can see that can abound more and more 1 Thessalonians 4:1 but I don't see any scripture about growing in Holiness, yet I see it repeated again and again...
You don't see the phrase "grow in holiness" but you do see may references to be separate, separate yourselves, purge yourselves, etc. You also see scriptures about light and that we need more and more light (revelation) from the Lord to help separate us from darkness.
In reading different posts I don't believe everyone is on the same "track" and that they may have different definitions for holiness.
If holiness is akin to a spiritual separation (light from darkness), then yes, light can be dim, yet grow brighter and brighter (until the noonday), dispelling (separating from) more and more darkness.
Psa_37:6 And he SHALL BRING FORTH (a process) thy righteousness as the light, and thy judgment as the noonday.
It takes several hours for the light of the sun to be at noonday.
2Pe_1:19 We have also a more sure word of prophecy; whereunto ye do well that ye take heed, as unto a light that shineth in a dark place, until the day dawn, and the day star arise in your hearts: (Again, we see a process. The sun does not come straight up to noon, in an instant. It gradually dispels the darkness).
Do you have a complete revelation of God when you are first saved? Do you have all the light you need, and have no blind spots (darkness) in your heart?
Holiness is indeed, separating yourself from the profane and walking in greater and greater light.
2Co_6:17 Wherefore come out from among them, and be ye separate, saith the Lord, and touch not the unclean thing; and I will receive you,
We are responsible for the light that God gives us and we receive more and more light (revelation) from Him as we hunger and thirst for righteousness.
Psa_36:9 For with thee is the fountain of life: in thy light shall we see light.
Psa_37:6 And he shall bring forth thy righteousness as the light, and thy judgment as the noonday.
Light is brought forth gradually in our lives just as it rises in the morning.
Pro_4:18 But the path of the just is as the shining light, that shineth MORE AND MORE unto the perfect day.
Psa_43:3 O send out thy light and thy truth: let them lead me; let them bring me unto thy holy hill, and to thy tabernacles.
Heb_7:26 For such an high priest became us, who is holy, harmless, undefiled, separate from sinners, and made higher than the heavens;
So, I am not saying that someone cannot be perfectly walking in the light that they have. There is a separation/sanctification process that is part of our walk down here and we are responsible to respond in faith to the increase of revelation (light) that the Lord brings to us. This faith response will bring a deeper separation, holiness unto the Lord.
Luk_3:17 Whose fan is in his hand, and he will THOROUGHLY PURGE (a process) his floor, and WILL GATHER (denoting another process) the wheat into his garner; but the chaff he will burn with fire unquenchable.
2Ti_2:21 If a man therefore purge himself from these, HE SHALL BE (another process) a vessel unto honour, SANCTIFIED, and meet for the master's use, and prepared unto every good work.