If the apostles didn't teach it.
Acts 17:11 These were more noble than those in Thessalonica, in that they received the word with all readiness of mind, and searched the scriptures daily, whether those things were so.
Even what the apostles taught should be checked with scripture. How much more the Catholic Church?
Sorry; that's not what the verse says.
Hey, Biblical Christian:
1) 1 Corinthians 11:2: “. . . keep the ordinances, as I delivered {them} to you.”
Do you keep these ordinances, delivered orally?
2) 2 Thessalonians 2:15: “. . . hold the traditions which ye have been taught, whether by word, or our epistle.”
Do you keep ALL of these traditions, including the ones taught by word of mouth?
3) 2 Thessalonians 3:6: “Now we command you, brethren, in the name of our Lord Jesus Christ, that ye withdraw yourselves from every brother that walketh disorderly, and not after the tradition which he received of us.”
Paul refers to a tradition given by him, which we must keep. Do you know what it is?
4) 1 Thessalonians 2:13: “. . . when ye received the word of God which ye heard of us, ye received {it} not {as} the word of men, but as it is in truth, the word of God, which effectually worketh also in you that believe.”
The word of God is something that Paul delivered orally.
5) Jude 3: “. . . ye should earnestly contend for the faith which was once delivered unto the saints.”
How can you contend for a faith entrusted to the apostles, if Jesus left no written words?
6) Rom 6:17 But God be thanked that [though] you were slaves of sin, yet you obeyed from the heart that form of doctrine to which you were delivered.
But you would ignore this doctrine, because it isn’t written. Too bad for you.
7) 1 Cor 11:23 For I received from the Lord that which I also delivered to you
Ditto.
8) Gal 1:9ff But even if we, or an angel from heaven, preach any other gospel to you than what we have preached to you, let him be accursed. As we have said before, so now I say again, if anyone preaches any other gospel to you than what you have received, let him be accursed.
Anyone who preaches something differing from the oral apostolic preaching is accursed.
9) 2 Pet 2:21 For it would have been better for them not to have known the way of righteousness, than having known [it,] to turn from the holy commandment delivered to them.
But never delivered to you, since you don’t receive oral teachings. Not from apostles, anyway.
10) Romans 10:15 And how shall they preach unless they are sent?
You believe preachers without authority, who were never sent.
11) 2 John 1:12 Having many things to write to you, I did not wish [to do so] with paper and ink; but I hope to come to you and speak face to face, that our joy may be full.
John prefers oral teaching to written.
12) Matthew 17:5 While he was still speaking, behold, a bright cloud overshadowed them; and suddenly a voice came out of the cloud, saying, “This is My beloved Son, in whom I am well pleased. Hear Him!”
Hear him.
13) Luke 10:16 “He who hears you hears me, and he who rejects you rejects me, and he who rejects me rejects him who sent me.
He said hears, not “reads”. And only those sent by him, not just anybody.
14) Luke 24:45 Then he opened their minds to understand the scriptures.
The apostles, not all of the baptized.
15) Matthew 13:11 And he answered them, “To you it has been given to know the secrets of the kingdom of heaven, but to them it has not been given
Ditto.
16) Luke 8:10 he said, “To you it has been given to know the secrets of the kingdom of God; but for others they are in parables, so that seeing they may not see, and hearing they may not understand.
Ditto.
17) 1 Timothy 3: 14-15 I hope to come to you soon, but I am writing these instructions to you so that, if I am delayed, you may know how one ought to behave in the household of God, which is the church of the living God, the pillar and bulwark of the truth.
The Church is the pillar and the bulwark. Not the bible.