'Sanctify' is an important practical Bible word with a straightforward meaning: 'to set apart for God's use'. Everybody who has received Christ is a child of God (John 1:12). And every child of God is included in His 'family business' (2 Timothy 2:15), to work with Him by drawing strength from Him. As they grow up in the family, they are being shaped by Him, so that they can serve Him in a way which brings Him glory. They are all saints, which means people who are being sanctified (1 Corinthians 1:2).
 
Sanctification is God's will for each of us. It is a process which requires His power and our cooperation. His power is unlimited; but cooperating will be a learning curve for every saint. An important part of our sanctification is how we deal with sexual passion. Naturally we will not get it right; the temptations are bigger than we are. We have to learn how to control passion, rather than allow passion to control us, because we belong to the Lord. It is not just about a moral code to follow but a relationship with God to develop.
 
Sexual sin is never a private matter; it always involves others. Within the fellowship, there should be a freedom of relationship between brothers and sisters, but that is spoiled by immorality as it would be in a human family. It offends God because it disturbs rightful relationships and prevents proper spiritual service. It also sets back His intended purpose of making us especially suitable for Him to use as lights in a dark world. His anger is against those who refuse to be sanctified, including in this area.
 
Many people find it difficult to cooperate with the Lord in controlling their bodies, and give up trying. They think that if it is so difficult it cannot matter that much. They are wrong. That short-term route to happiness will rob us and others of joy, and will frustrate the grace of God. It sets back the process of sanctification. The way ahead is to recognise the seriousness of God's instruction, repent of failure, be reconciled with those who have been offended, and ask Him for grace to learn a new self-discipline - the fruit of our willingness to cooperate with His Spirit's presence (Galatians 5:22-23).