Matt 28:19 - 20
19 Go out and train everyone you meet, far and near, in this way of life, marking them by baptism in the threefold name: Father, Son, and Holy Spirit. 20 Then instruct them in the practice of all I have commanded you. I'll be with you as you do this, day after day after day, right up to the end of the age."

This verse is being used by Churches for baptism ONLY but there is much more to this than baptism. Baptism is called I this verse a “marking”. A marking of what?