Why are the words of Paul considered Scripture, and does he contradict the words of Jesus?
The 13 epistles written by the apostle Paul most certainly are Scripture, breathed out from God through the human author without error. The apostle Peter recognized Paul's writing at Scripture within one of his own letters: "Our dear brother Paul also wrote you with the wisdom that God gave him. . . . His letters contain some things that are hard to understand, which ignorant and unstable people distort, as they do the other Scriptures, to their own destruction" (2 Peter 3:15–16). Peter's description of Paul's letters as "the other Scriptures" classifies Paul's writings with the Old Testament—the "other Scriptures" that would have been available to a first-century followers of God (see 2 Tim. 3:16).
At least four times in Paul's writings he indicates that he is writing what he has received from Jesus (emphasis added): "To the married I give this command (not I, but the Lord): A wife must not separate from her husband" (1 Cor. 7:10); "For I received from the Lord what I also passed on to you" (1 Cor. 11:23); "For what I received I passed on to you as of first importance: that Christ died for our sins according to the Scriptures" (1 Cor. 15:3); and "I want you to know, brothers and sisters, that the gospel I preached is not of human origin. I did not receive it from man, nor was I taught it; rather, I received it by revelation from Jesus Christ" (Gal. 1:11–12).
Twice in Scripture we have an account of Paul quoting Jesus' words. "The Lord Jesus himself said: 'It is more blessed to give than to receive'" (Acts 20:35). In 1 Timothy 5:18, Paul quotes the words of Jesus found in Luke 10:7: "The worker deserves his wages." It seems then that Paul carefully and faithfully passed on Jesus' words in his writings—writings that come from the very mouth of God.