Romans 8:16 asserts, “The Spirit himself bears witness with our spirit that we are children of God.” What does this verse mean?
The verb “bears witness with” is all one word in the Greek (summartureō), a combination of the preposition “with” (sun) and the verb “to bear witness” (martureō). Paul uses this verb only two other times. First, in Romans 2:15, just as one’s good actions are one witness to the work of the law on the heart, the “conscience also bears witness” to the rightness or wrongness of these actions. Second, in Romans 9:1, just as Paul claimed that he himself spoke the truth, so also he affirmed this truth by asserting, “my conscience testifies with me in the Holy Spirit” (NASB95).
Just as we see a double witness in both Romans 2:15 and 9:1, so also we see two witnesses in Romans 8:16. One witness is the Holy Spirit. The other witness is the Christian’s spirit. The content of this double witness is clearly stated: “that we are the children of God.” When our own spirit witnesses within us that we are the children of God, we consequently “cry, ‘Abba! Father!’” (Rom 8:15). But how exactly and to whom the Holy Spirit bears witness are matters over which good people disagree.
Some emphasize a witness by the Spirit that is externally manifest for the Christian to see. In context, the Christian “by the Spirit” chooses to “put to death the deeds of the body” and lives a life “led by the Spirit of God” (Rom 8:12–13). Thus, the Spirit’s witness is a transformed life, something that would only be true of a son of God.
Others understand the Holy Spirit’s witness as something internal, something from the Spirit to the Christian alone. Romans 8:15 identifies “the Spirit of adoption” as the One “by whom we cry, ‘Abba! Father!’” Then, though no formal language connects Romans 8:15 to 8:16 (e.g., “because” or “for”), Romans 8:16 could nonetheless function to explain how the Spirit enables such a cry—by witnessing with the Christian’s spirit that he is a son of God. So, the Spirit witnesses with and somehow to the Christian that he is a son of God. As a result, the Christian will naturally “cry, ‘Abba! Father!’” (Rom 8:15). In this understanding, what is left unstated is how exactly the Spirit witnesses to the Christian’s spirit. A cessationist must see this witness as non-revelatory, and this witness could be described as mystical in the sense that it cannot be explained.
The Spirit’s saving work within a believer inevitably shows itself tangibly in that person’s life—the Spirit liberates the believer in Christ Jesus from sin and leads him to live a righteous life (cf. Rom 8:1–13). This Spirit-led obedience to Christ is one means of assuring him that he is a son of God. Additionally, Romans 8:16 could be understood to teach that the Spirit internally assures the Christian of his spiritual sonship, resulting in his cry to the Father above.
