For this blogpost you will want to look up Eph. 4:22-24 and Col. 3:9-10. I consider these two passages to be a definitive starting point for discussion of the “how to” or mechanics of sanctification. As you will see, the Word of God gives some general instruction but does not explain exactly how to gain victory in each specific area of behavior. More on this later.
Sanctification involves growth in three areas: holiness, righteousness, and knowledge. Growth in holiness involves separation from the defilement of sin and is performed through the putting off of the old man. Growth in righteousness involves replacing sinful behavior patterns (thoughts, words, deeds) with upright behaviors and is performed through putting on the new man. Growth in knowledge involves changes in thinking (repentance) about who God is, who we are in relation to Him, what He wills for us, and the nature of reality in general. Growth in knowledge is performed through the renewing of the mind.
This is not rocket science. In fact Paul gives several examples to illustrate the mechanics of sanctification, but I will cite one: Let him who stole steal no longer, but rather let him labor, working with his hands what is good, that he may have something to give to him who has need (Eph. 4:28). If you are a converted thief, growth in holiness means you put off the old man and stop stealing. Growth in righteousness means you put on the new man and replace stealing with the honest earning of money. Notice, the Bible does not spend any time telling us how to stop stealing. Why? Because as a believer you do not need to be told how to stop stealing. Scripture assumes that as a regenerate child of God you have all the ability and ingenuity you need to stop stealing. You sin because you want to sin and choose to sin. No one twists your arm and drags you kicking and screaming into sin. If you are a born again thief you can stop stealing if you want to. If you are a drunk or a fornicator or a liar or a glutton you can stop if you want to with no instruction in how to stop. Your sinful habits are not diseases over which you are powerless. This doesn’t mean it will be easy; but do not be deceived by the wimpy non-Christian 12-step/disease/idiocy of the world. Do not call God a liar–He says you can stop (1 Cor. 10:13).
What about growth in knowledge, or the renewing of the mind? I believe this takes two forms. First there is the daily re-conditioning of our thinking through reading, study, meditation, hearing, and discussing the Word. Just like a daily shower a steady consistent exposure to the Word has a cleansing sanctifying effect (John 17:17). In addition to this there is the specific restructuring of fleshly thought patterns that accompany and justify sinful behavior. I believe this is hinted at in the example given above. The thief is told to stop stealing and start working. Why? So that he will be able to share with others in need. This is a purpose clause in Greek, and denotes the purpose of working instead of stealing. It gets at the root of what our work ethic and motive should be.
What are the thought patterns of a thief? Is he thinking of others? Well, usually no. He accustomed to easy money which he can lavish upon himself. Certainly he is not concerned for the hardship he is causing his victims. When the thief stops stealing and starts working he is to adopt a new way of thinking, one reflected in the statement of Jesus that it is more blessed to give than receive. When a man works hard to earn money to provide for the needs of his family, and he takes pride in being a responsible breadwinner, he is then thinking in a way that is a delight to the Lord. Can you see the difference in thinking between the thief and the hard-working provider? This kind of shift in thinking is at least part of what Paul is alluding to when he speaks of the renewing of the mind. Of course this concept is comprehensive, and includes theological indoctrination as well.
Finally, all this takes work (Phil. 2:12-13). There are no shortcuts. It takes daily consistent effort over the long haul.
I hope this short discussion will prove helpful and motivating to you as you seek to grow in the Lord. For more, see my video series on sanctification.