Correction: OSAS does not teach that. Calvinists teach that.
Jesus taught that believer have eternal life in John 5:24. He also taught that recipients of eternal life shall never perish in John 10:28.
It's not difficult to connect the dots here. Once given the gift of eternal life, the recipient shall not (cannot) perish.
In Matt 7:21-23, what is clear is that the crowd had never believed, as you correctly note. Their entire appeal for entering the kingdom is based on what THEY did for Him, not what He did for them. Which is a big difference.
Jesus taught that believer have eternal life in John 5:24. He also taught that recipients of eternal life shall never perish in John 10:28.
It's not difficult to connect the dots here. Once given the gift of eternal life, the recipient shall not (cannot) perish.
In Matt 7:21-23, what is clear is that the crowd had never believed, as you correctly note. Their entire appeal for entering the kingdom is based on what THEY did for Him, not what He did for them. Which is a big difference.
But some people - such as the OP, make the mistake of thinking those who were given such a gift have the desire, when filled with God's Holy Spirit, to commit grievous sin.
God's people, while they may make mistakes and have some minor sins in their life they are working to overcome with God's help, aren't ever going to run around murdering and whoremongering etc.. that is your sign they don't belong to God, because we are OF our respective father, whether that father be God or the devil.