Let every one, then, see to it that he esteem this commandment great and high above all things, and do not regard it as a joke. Ask and examine your heart diligently, and you will find whether it cleaves to God alone or not. If you have a heart that can expect of Him nothing but what is good, especially in want and distress, and that, moreover renounces and forsakes everything that is not God, then you have the only true God. If on the contrary, it cleaves to anything else, of which it expects more good and help than of God, and does not take refuge in Him, but in adversity flees from Him, then you have an idol, another god. In order that it may be seen that God will not have this commandment thrown to the winds, but will most strictly enforce it, He has attached to it first a terrible threat, and then a beautiful, comforting promise which is also to be urged and impressed upon young people, that they may take it to heart and retain it: [Exposition of the Appendix to the First Commandment.] For I am the Lord, thy God, strong and jealous, visiting the iniquity of the fathers upon the children unto the third and fourth generation of them that hate Me; and showing mercy unto thousands of them that love Me and keep My commandments. Although these words relate to all the commandments (as we shall hereafter learn), yet they are joined to this chief commandment because it is of first importance that men have a right head; for where the head is right, the whole life must be right, and vice versa. Learn, therefore, from these words how angry God is with those who trust in anything but Him, and again, how good and gracious He is to those who trust and believe in Him alone with the whole heart; so that His anger does not cease until the fourth generation, while, on the other hand, His blessing and goodness extend to many thousands lest you live in such security and commit yourself to chance, as men of brutal heart, who think that it makes no great difference [how they live]. He is a God who will not leave it unavenged if men turn from Him, and will not cease to be angry until the fourth generation, even until they are utterly exterminated. Therefore He is to be feared, and not to be desisted.