The First Commandment teaches us to trust in Christ alone for justification, sanctification, and eternal life.
- The First Commandment reads (I’m using NASB throughout): “You shall have no other gods before Me.” Obviously, trusting in someone or something else (even one’s own good works) for justification, sanctification, and eternal life” is to have another god beside the true God. It is a rejection of Jesus and his work. It is a violation of the First Commandment.
- As a matter of the historic record, at the time of the Reformation, that Protestants invoked the First Commandment precisely for the purpose of defending the doctrine of sola Christo and thus of sola fide. The took the First Commandment as a condemnation of Rome’s superstitions and her teaching of salvation by works. For example, consider the Heidelberg Catechism
Q94: What does God require in the first Commandment?
A94: That, on peril of my soul’s salvation, I avoid and flee all idolatry, sorcery, enchantments, invocation of saints or of other creatures; and that I rightly acknowledge the only true God, trust in Him alone, with all humility  and patience  expect all good from Him only, and love, fear  and honor  Him with my whole heart; so as rather to renounce all creatures than to do the least thing against His will.
1. I Cor. 10:7, 14
2. Lev. 19:31; Deut. 18:10-12
3. Matt. 4:10; Rev. 19:10; 22:8-9
4. John 17:3
5. Jer. 17:5
6. I Peter 5:5-6
7. Heb. 10:36; Col. 1:10b-11; Rom. 5:3-4; I Cor. 10:10
8. Psa. 104:27-30; Isa. 45:6b-7; James 1:17
9. Deut. 6:5
10. Deut. 6:2; Psa. 111:10; Prov. 9:10; Matt. 10:28
11. Deut. 10:20
12. Matt. 5:29-30; 10:37; Acts 5:29
(a) Notice the prooftext for the demand that we “rightly acknowledge the only true God” is John 17.3: “And this is eternal life, that they may know Thee, the only true God, and Jesus Christ whom Thou hast sent.” The other New Testament texts are interesting as well.
(b) Notice also that this Christian (see question #1) is told that disobeying the First Command will emperil his or her salvation. If the First Commandment does not teach us to trust in Christ alone then this would be problematic.
(c) Finally, notice the mention of the invocation of the saints. The First Commandment was not only about never sinning, it was about trusting the true God and mediator to deal with your many continual sins. The Roman Catholics rationalized prayers to the saints and hope on their merits. The Protestants said that we should pray to and trust in Christ alone. And they used the First Commandment to prove this.
- Having no other gods before Yahweh meant never sacrificing animals to any other god but Him. This is not only the obvious context of Exodus and the Pentateuch, but only a few sentences after the giving of the decalogue God gives instructions on how to properly sacrifice “ascension offerings and peace offerings.” These sacrifices pointed to Christ. The First Commandment teaches us to trust in Christ alone for justification, sanctification, and eternal life.
- The fact that neither unfallen Adam, nor Christ, needed to be forgiven is entirely irrelevant. The First Commandment tells us to trust in God alone for all that we need. For us sinners, that means that we must trust in Christ alone for justification, sanctification, and eternal life. For Jesus it meant trusting the Father for vindication, growth in grace (Luke 2.51), and resurrection to glory. If we need it, then the First Commandment tells us to look for God as he has revealed his will in reference to that need. We need justification, sanctification, and eternal life. Those can only be found in Christ. Christ is true God as well as true Man. Thus, the First Commandment teaches us to trust in Christ alone for justification, sanctification, and eternal life.
- The Ten Commandments are part of the administration of the covenant of grace. They were not stipulations given to sinless beings in which they were expected to persevere in perfect obedience. They are stipulations given to sinners expected to constantly sin. When an Old Testament Hebrew sacrificed to Baal in order to receive the forgiveness of sins, he was violating the First Commandment. When a Church member decides to pray to the god of the Mormons for the forgiveness of sins, he is violating the First Commandment. The First Commandment teaches us to trust in Christ alone for justification, sanctification, and eternal life.
- Thus the preamble to the Decalogue makes it clear that the Ten Commandments are given for the saved community to live by faith in God’s grace. “I am the Lord your God, who brought you out of the land of Egypt, out of the house of slavery.” Thus, the Westminster Shorter Catechism teaches:
Q44. What doth the preface to the Ten Commandments teach us?
A44. The preface to the Ten Commandments teacheth us, That because God is The Lord, and our God, and Redeemer, therefore we are bound to keep all His commandments [Deut. 11:1; Luke 1:74-75].
The Decalogue explicitly appeals to God as Redeemer, the one who frees God’s elect from all sin and brings them into an esate of salvation (See question 20 and then 21 of the Westminster Shorter Catechism).
I can only hope this brief post is totally superfluous for most readers. As usual, Francis Turretin’s wisdom is worth reading today:
Although faith in Christ (which is prescribed in the gospel) can be called new in respect of its object (which is revealed in the gospel alone), still it belongs to the law in respect of act and of obligation because we are bound to believe in God and all his word. Repentance also belongs to the law; not as it was made for the first man, but as repeated for the sinner and illustrated by the gospel; and materially, if not formally, because it teaches and prescribes the mode of repentance