This is a faithful saying, and these things I will that thou affirm constantly, that they which have believed in God might be careful to maintain good works. This appears from the order laid down by God himself in delivering the moral law from mount Sinai. And let it be remembered, that the Apostle Paul calls gospel-obedience the obedience of faith, as springing from and founded upon faith. And if we examine the order of doctrine laid down in all his epistles, we shall find, that he first propounds the doctrine of faith, or what man is to believe, and upon that foundation inculcates the duties that are to be practised. That all works without faith are dead, and so cannot please God.
Faith is the principle of all holy and acceptable obedience.
The Beauties of Boston a list of other extracts from Thomas Boston here at Fire and Ice.