'Pouring out the vials upon the earth, which contained the plagues,' in Revelation 16:1, signifies influx of the reformed into the church, or into people who study and receive the doctrine of justification by faith alone.

(Referencat: Apocalypse Explained 16; Apocalypse Revealed 676)

In the Word, people who trust in themselves and their own intelligence are sometimes called 'strong,' as in Isaiah 1:31. This is because they themselves and their work is strong.

(Referencat: Apocalypse Explained 504)