21 when you heard about Christ and were taught in him in accordance with the truth that is in Jesus.

Read Ephesians 4:21 Using Other Translations

If so be that ye have heard him, and have been taught by him, as the truth is in Jesus:
assuming that you have heard about him and were taught in him, as the truth is in Jesus,
Since you have heard about Jesus and have learned the truth that comes from him,