III. Concerning the sinfulness of man's heart, and the divine inspection it is always under, v. 9, 10. It is folly to trust in man, for he is not only frail, but false and deceitful. We are apt to think that we trust in God, and are entitled to the blessings here promised to those who do so. But this is a thing about which our own hearts deceive us as much as any thing. We think that we trust in God when really we do not, as appears by this, that our hopes and fears rise or fall according as second causes smile or frown.