What is a saint? Many people think your behavior has to be extra holy in order to be a saint. This view is not supported by Scripture.
The apostle Paul addresses all believers as saints. Does this mean that all believers at that time in history were extra holy? Certainly not.
The people in Ephesus were well known for their involvement in the occult. Many of the believers there were still under that influence. In fact, it wasn’t until a good scare they (the believers) got from a case of demon-possession that they gathered their occult paraphernalia together and burned it. Yet Paul called them saints.
The believers at Corinth would hold communion often just so that they could get drunk. Yet Paul calls them saints.
Since the Bible is also written to us believers today, we are called saints. God’s righteousness is gift, not something we earn.