Paul left off telling the Church that you will know a true believer not by what they say, but by Who their following, as genuine believers are led by The Spirit of God and not by the whims and cares of this world. He is not talking about performing spectacular feats of bravery, or remarkable acts of the supernatural, instead he says V15 there is a gentle leading out of bondage, away from fear, and into a real experience of joy. Then V16 says we’ll embrace true assurance, as God’s Spirit bears witness to our spirit that we are is children, amazing!