Whoever respects his parents in life
CHAPTER II: THE CRITERIA THAT SHOW WHICH COMMANDS BELONG TO THE MORAL LAW
§ 6. Therefore, since the moral Law is separated from the others by so great a difference, one must accurately note which commandments belong to the moral Law and which are merely ceremonial and forensic. There are two main criteria by which this can be understood and investigated. The first is the light of nature still remaining in our inborn ideas. For whatever agrees with the natural ideas grafted into the minds of men at creation and still partly left after the fall belongs to the moral Law. Thus the more sensible heathen approve of honoring one’s parents, and this agrees with the very law of nature. The verses of Euripides are well-known:
Whoever respects his parents in life
Is dear to the gods while he lives and when he dies.1
Therefore the commandment to honor one’s parents is moral.
The second criterion is the light of grace set forth in the exposition of Moses and the prophets and especially of Christ and of the apostles in the New Testament. You see, because our natural knowledge has been badly dimmed through sin, the light of nature is not bright enough to decide the matter. The light of grace must be added and kindled in us through the sermons of the prophets and apostles. Therefore this rule is added: whatever Moses and the prophets show as pertaining not only to the Israelites but to all nations, those are the commandments of the moral Law. In this way, laws to be observed concerning respect for blood relation in marriages belong to the moral Law, as is gathered from the fact that Moses clearly adds in Lev. 18:24 that the Canaanites had to be punished by God for transgressing those laws. So also when the prophets preach from the Law against common vices of the Gentiles, then it is sure that those prohibitive mandates belong to the Decalogue. In the New Testament, a brighter light of this knowledge is given through Christ and the apostles, for whatever is repeated and commanded in the New Testament and belongs to all nations belongs to the moral Law and is binding upon all people. However, here one must note the exception of the apostles in the sprouting of the New Testament church, who observed and ordered to be observed abstinence from blood and from what had been strangled as well as the rite of circumcision (Acts 15:29; 16:3; 21:26). This was not because they believed that those things belonged to the moral Law and applied to all Christians of all times and all places. Rather, [they did this] to give an honorable burial to the Jewish synagogue, lest any cause for offense might be given to the weak by the untimely use of Christian liberty, that is, so that the sensibilities of the Jews who had been converted to Christ might not be put off and so that the bond of harmony between those converted from the Jews and from the Gentiles might not be broken. Lyra (on Acts 15): “That which had been strangled and blood were indeed lawful foods, but for the sake of friendly unity they wrote to the Gentiles that they should abstain from such foods, just as it frequently happens that one will abstain from a food which he knows to be loathsome to his friend.” But as time passed, when the cause ceased, the effect also ceased, as the truth of the teaching of the Gospel was made manifest.
1 Fragment 852 (LCL 506 [2008], 478–79).