WELS affirms the principle of sola scriptura—Scripture alone is the supreme norm and ultimate authority for faith and practice. Scripture is complete, authoritative, and sufficient for all matters of doctrine and conduct. God's revelation is closed; no additional revelation is being given in the present age.

While WELS honors Christian tradition and the Lutheran confessions as faithful summaries and interpretations of Scripture, these remain always subordinate to Scripture itself. When tradition and Scripture conflict, Scripture must be obeyed. The confessions are helpful guides for understanding Scripture but carry no independent authority.

WELS explicitly rejects ongoing prophecy, private revelation, visions, or any claim that God is continuing to reveal new doctrines or practices. The gifts of apostolic prophecy and direct revelation ceased with the completion of the New Testament canon. The Holy Spirit works in the present age through the proclamation and teaching of the Word, through the sacraments, and through the application of Scripture to life. WELS opposes all forms of modern revelations, whether from Mormonism, Christian Science, or charismatic movements claiming new prophetic words.