For. — “For, in fact,” (supporting and exceeding the statement of 1 Thessalonians 1:7 about Greece) “you form the centre from which the doctrine of Christ has rung (not rang) out like a trumpet through those countries; and even beyond, your faith is well known.” The clauses are not quite logically balanced.
Your faith does not mean “your creed,” but “the report of your extraordinary faith.”
To say anything — i.e., about our success at Thessalonica.