The word sanctification comes from the Greek word “hagiasmos” and is defined as consecration or purification of one’s heart and life. It is derived from two Latin words: sanctus which means holy and fiacre which means make. In Romans 1-5, Paul describes the act of being justified before God but then makes the switch to speaking about sanctification in Romans 6.
The two terms are often confused but there is a substantial distinction between them. Justification deals with the penalty for sin while sanctification deals with the power of sin; justification is how God works in the unsaved and sanctification is how God works with the saved. It can be said, justification gives people hope for the future, but sanctification is how they transform the way they live until they attain that hope.
When a person accepts the gift of salvation, they are immediately forgiven and set apart but that is just the beginning. They then spend the rest of their lives growing in the knowledge of God’s will as the Spirit works to mold them into the image of Christ.