The consistency between how Jesus tells us to live in the Gospels and how the various New Testament epistles tell us to live makes both sets of texts more credible, does it not?
This occurred to me during our pastor’s sermon this week, which focused Paul’s letter urging the Colossians to forgive one another as God had forgiven them (Colossians 3:13). That injunction, of course, is at the heart of the Lord’s Prayer (Matthew 6:12), which in turn is at the heart of the Sermon on the Mount. Now, either Paul was told by someone else that Jesus said this, or Paul got this directly from God (Jesus told him or the Holy Spirit inspired him). But either way this makes it more likely that Jesus really said it (that is, the the Sermon on the Mount was accurately reported by Matthew, and the Sermon on the Plain by Luke) and that Paul’s letters deserve their status as Scripture.
Consider this point more broadly: Suppose that the epistles were filled with moral injunctions that were at odds with what Jesus taught us in the Gospels. That would make it harder to believe either and impossible to believe both. But we don’t have that. Instead we have deep moral teachings from multiple writers that are strongly consistent. And in Acts, in one of the relatively rare instances where Jesus is quoted outside the Gospels, it still sounds just like Him: “It is more blessed to give than to receive” (Acts 20:35). There’s a lot more coordination going on here than you’d expect from a bunch of unhinged liars scattered about the ancient Mediterranean making stuff up. You have a whole lot of people somehow reading off the same script, changing their beliefs and faith, and their actions and lives — and in many instances following this new script all the way to death. How does that happen, unless the Christian explanation for these writings, these texts — and the Truth they tell — is the right one?
Final note: And couldn’t a similar observation be made about the consistency of the messages within the Old Testament — and across the Old Testament to the New?