What is sanctification? Is progressive sanctification biblical?

Scripture is clear that believers (as people) were sanctified – past tense – the moment we were saved (1 Corinthians 6:11; Hebrews 10:10). This means we have been fully set apart for God. Our behavior, on the other hand, is being sanctified (set apart) as we learn and grow in our understanding of God’s grace (1 Peter 1:15). We must separate who we are (sanctified children of God) from how we perform (a mix of walking by the flesh and walking by the Spirit) to rightly understand this issue. Unfortunately, the popular idea of “progressive sanctification” conflates these two types of sanctification and practically ignores what has already been done within us.