And beginning with Moses and all the Prophets, he explained to them what was said in all the Scriptures concerning himself.[Luke 24:27]
When the Christ met two ppl on the Emmaus road, when He taught them about all things concerning Himself, He used solely the scriptures to teach them.
But as for you, continue in what you have learned and have become convinced of, because you know those from whom you learned it, and how from infancy you have known the Holy Scriptures, which are able to make you wise for salvation through faith in Christ Jesus. All Scripture is God-breathed and is useful for teaching, rebuking, correcting and training in righteousness, so that the servant of God may be thoroughly equipped for every good work.[2 Timothy 3:14-17]
Paul is instructing Timothy here to not stray from the word of God. Because, they are what makes a man wise concerning salvation, makes him equipped for every good work, how to teach, &c.
Synods, confessions, creeds, church councils, all these are good and necessary to expound upon the scriptures, but they do not usurp them. The scriptures are our sole authority in all things concerning God.