How do we know that God’s sanctification is complete?

The doctrine of sanctification in the Bible is expressed clearly in Hebrews 10, where the writer emphasizes that we are sanctified through the body of Jesus Christ once for all. This indicates that sanctification is not a progressive work dependent on human efforts but rather a completed act by Christ that does not require repetition. The passive tense of the term 'sanctified' highlights that it is God who performs this act upon believers, declaring them holy and set apart for His purposes. This means that all who are united with Christ have been perfected in Him, thus stripping away their sins and leaving only holiness in the sight of God. As such, sanctification is solely God's work, made possible through the finished work of Christ on the cross.