Paul, an apostle (special messenger) of Christ Jesus (the Messiah), by the divine will (the purpose and the choice of God) to the saints (the consecrated, set-apart ones) at Ephesus who are also faithful and loyal and steadfast in Christ Jesus: Ephesians 1:1(AMPC)
The wedding attire is designed, made, meant and put on for a specific and special occasion, function and moment – the wedding celebration.
You don’t put on a wedding dress to work in a garage, run a marathon, or do plumbing work. That garment is set apart for the wedding function.
Likewise a saint is someone who is called out from the world and set apart for God. He’s called and separated from the world’s common way of thinking, seeing, acting and living to God’s way of thinking, seeing, acting and living.
Through Faith in Christ Jesus we are called out from the world and set apart for God. We are made saints through Jesus’ death and resurrection.
As set apart-ones for God we ought to live to honor and glorify Him on every occasion at all times by showing forth His nature and character in us.