Similar to the 2nd Mandate‘s addressing of slander, the third mandate is about speaking the truth. The initial command is “love the truth, and let nothing but truth proceed from your mouth.” The reasoning behind this command is then given:
that the spirit which God has placed in your flesh may be found truthful before all men; and the Lord, who dwelleth in you, will be glorified, because the Lord is truthful in every word, and in Him is no falsehood. They therefore who lie deny the Lord, and rob Him, not giving back to Him the deposit which they have received. For they received from Him a spirit free from falsehood. If they give him back his spirit untruthful, they pollute the commandment of the Lord, and become robbers.
In other words: hey, we’re Christians; we say that God is in us, but if lies are coming out of us, it looks like God’s lying. And since we’re always in God’s presence, we’re lying before God, abusing his Spirit within us. Misusing the gift of the Spirit is likened to robbing God. This thinking is similar to James when he wrote that committing one sin makes you guilty of breaking the entire law.
At this news, Hermas breaks down and weeps because “he doesn’t know if he “can be saved” because he’s had a bad history of lying. “How then can I live, since I have acted thus?” Fortunately there’s a gospel for the sinner! The shepherd-angel tells him that although he has indeed grieved the Holy Spirit, it’s still possible for him to redeem his past and “obtain life.” Once again there’s that language of “obtaining” salvation, which may make an Evangelical twitch in pain. But Paul uses this language too, from time to time. The focus isn’t on earning salvation, but simply the idea of getting there. Remember, “getting saved” in its fullest sense is not merely a past event, but a life-long process with an awaited promise in the resurrection. In fact, this mandate ends with a gospel proclamation: “whosoever shall hear this commandment, and depart from that great wicked falsehood, shall live to God.”