[Elsie]

The bible does not say that it is itself the only source of truth.

The Bible DOES give warning to all:

1 Corinthians 4:6

Now, brothers, I have applied these things to myself and Apollos for your benefit,

so that you may learn from us the meaning of the saying, "Do not go beyond what is written."

Then you will not take pride in one man over against another.

[St_Thomas_Aquinas]

Now, brothers, I have applied these things to myself and Apollos for your benefit, so that you may learn from us the meaning of the saying, "Do not go beyond what is written." Then you will not take pride in one man over against another.

--St. Paul

"So then, brothers and sisters, stand firm and hold fast to the teachings we passed on to you, whether by word of mouth or by letter.

--St. Paul

So how do we reconcile these verses?

According to St. Thomas Aquinas, Paul was saying that one doesn't need to go beyond the passage in Wisdom teaching that pride is to be avoided.

"And they shall fall after this without honour, and be a reproach among the dead for ever: for he shall burst them puffed up and speechless, and shall shake them from the foundations, and they shall be utterly laid waste: they shall be in sorrow, and their memory shall perish."

--Wisdom 4:19

Paul is exhorting these Christians against factionalism. This becomes clearer in the latter half of the chapter.

I am writing this not to shame you but to warn you as my dear children. Even if you had ten thousand guardians in Christ, you do not have many fathers, for in Christ Jesus I became your father through the gospel. Therefore I urge you to imitate me. For this reason I have sent to you Timothy, my son whom I love, who is faithful in the Lord. He will remind you of my way of life in Christ Jesus, which agrees with what I teach everywhere in every church.

Some of you have become arrogant, as if I were not coming to you. But I will come to you very soon, if the Lord is willing, and then I will find out not only how these arrogant people are talking, but what power they have. For the kingdom of God is not a matter of talk but of power. What do you prefer? Shall I come to you with a rod of discipline, or shall I come in love and with a gentle spirit?

--St. Paul (1 Cor. 4)

Finally, your interpretation of Paul's saying proves too much. Since Paul was speaking of the Old Testament, your interpretation of this passage would prove the sufficiency of the Old Testament.

1 CORINTHIANS 4:6 AS A SUPPOSED PROOFTEXT FOR SOLA SCRIPTURA