And the very next section says this: "...no one can know with a certainty of faith, which cannot be subject to error, that he has obtained the grace of God." So that statement in fact contradicts salvation by grace through faith. And then later:
"...it is to be maintained, that the received grace of Justification is lost, not only by infidelity whereby even faith itself is lost, but also by any other mortal sin whatever, though faith be not lost".
So this is NOT the biblical doctrine of justification by grace through faith.