The Old Testament often repeated the command to Be holy as the Lord God is holy. The New Testament is clear that this applies to us also (1 Peter 1:16). But how do we become holy in that way?
Of course we stay back from sin. I'm here considering times when we have done that, but still do not find ourselves having become a fountain of God-pleasing graceful thoughts, words, and actions.
When the New Testament repeats the Levitical command to be holy, we do get some guidance, both in resisting our sinful tendencies, and in devoting ourselves to the brotherly love of fellowship (see 1 Peter 1).
I'd also consider the Sabbath as a help for holiness. The Sabbath is a holy day, not because work is bad, not because work is illegitimate, but because the blessings of God deserve a time of focus. The Sabbath is especially useful for gratitude and for rest. Busy-ness can be opposed to holiness. So can tiredness and stress. And I'll speak for myself here that rest can be an act of faith: a recognition that my busy-ness is not always the solution, an act of trust that God is, after all, God.
In the Bible we see that some "most holy" things can convey some holiness from God, as a bridge between God's ultimate holiness and this world. (Deeper dive here.) In the current Christian culture it's probably useful to add that book study is not the only means of time with God. Prayer and meditation, gratitude, and fellowship are worthy pursuits. For any who would hesitate about fellowship, consider the apostle Paul's blessing of "the grace of our Lord Jesus Christ, the love of God, and the fellowship of the Holy Spirit." I read that to mean both the fellowship with the Holy Spirit, and with each other through the Holy Spirit. It is a help to holiness when we listen to another person's cares, or otherwise arrange to be present in a way that encourages and uplifts.
