Tradition
1 Timothy 3:15
That thou mayest know how thou oughtest to behave thyself in the house of God, which is the church of the living God, the pillar and ground of the truth.
Context of the passage
Paul writes to Timothy about proper order and leadership qualifications within the Church community.
Catholic reading
Scripture itself calls the Church, not the Bible alone, the 'pillar and ground of the truth,' indicating that Christ established a living teaching authority to safeguard and interpret revelation reliably.
Common objection
The Church merely upholds and displays a truth found in Scripture alone; it doesn't generate doctrine or interpret authoritatively.
Response
A 'pillar' holds something up so it does not collapse; if Scripture alone were sufficient and self-interpreting, there would be no need for a structural support, which is precisely the teaching role the Magisterium fulfills.