Jesus established it when He said *It is written......*.
John 8:47 Whoever is of God hears the words of God. The reason why you do not hear them is that you are not of God.”
John 12:48 The one who rejects me and does not receive my words has a judge; the word that I have spoken will judge him on the last day.
John 14:23-24 Jesus answered him, “If anyone loves me, he will keep my word, and my Father will love him, and we will come to him and make our home with him. Whoever does not love me does not keep my words. And the word that you hear is not mine but the Father's who sent me.
John 17:17 Sanctify them in the truth; your word is truth.
Romans 10:17 So faith comes from hearing, and hearing through the word of Christ.
2 Corinthians 4:2 But we have renounced disgraceful, underhanded ways. We refuse to practice cunning or to tamper with God's word, but by the open statement of the truth we would commend ourselves to everyone's conscience in the sight of God.
Ephesians 6:17 .. and take the helmet of salvation, and the sword of the Spirit, which is the word of God,...
Hebrews 4:12 For the word of God is living and active, sharper than any two-edged sword, piercing to the division of soul and of spirit, of joints and of marrow, and discerning the thoughts and intentions of the heart.
God's word is truth. Why isn't the very words of God enough that Catholics feel the need to add to them and to disparage and down play them and say they aren't good enough?
God's very words to us aren't good enough? Really?
Why on earth, then, are you adding to them in your post?
I think the primary reason is so that the words of their magesterium and their "traditions" can be placed ABOVE the Scriptures in authority. They aren't alone in this faulty thinking, though. That's why we hear on these threads from so many about how we must thank the Catholic Church for our Bible because "they" wrote it, preserved it, compiled it, copied it and translated it and, without them, we wouldn't even HAVE a Bible. All poppycock, of course, but it seems to be the standard answer whenever the subject of the sufficiency of the Scriptures comes up.
I suspect the reasoning behind such talk is that they read what some of the Scriptures we post say and they can understand clearly enough that either the Scripture is wrong or their church is. Some of us decided it was the church and not the Bible. Others haven't gotten there yet - if ever - so they cling to their church in the hopes that someone will have a logical explanation for the contrast. Sadly, there will ALWAYS be someone around eager to do that and it's surprising how little it takes to settle them down (read some of the ScriptureCatholic references for a taste).
I'm so glad God found me and opened my eyes to the truth of the Gospel. He can do it for anyone who diligently seeks him.