Concerning the divine and sacred Mysteries of the Faith, we ought not to deliver even the most casual remark without the Holy Scriptures; nor be drawn aside by mere probabilities and the artifices of argument. Do not then believe me because I tell thee of these things, unless thou receive from the Holy Scriptures the proof of what is set forth: for this salvation, which is our faith, is not by ingenious reasonings, but by proof from the Holy Scriptures....In these articles we comprehend the whole doctrine of faith….For the articles of the Faith were not composed at the good pleasure of men, but the most important points chosen from all Scriptures, make up the one teaching of the Faith….This Faith, in a few words, hath enfolded in its bosom the whole knowledge of godliness contained both in the Old and New Testaments. Behold, therefore, brethren and hold the traditions (2 Thes. 2:15) which ye now receive, and write them on the table of your hearts....Now heed not any ingenious views of mine; else thou mayest be misled; but unless thou receive the witness of the prophets concerning each matter, believe not what is spoken; unless thou learn from Holy Scripture....receive not the witness of man.
Cyril of Jerusalem was a bishop of one of the most important sees of the church and responsible for instructing catechumens in the faith. No clearer concept of sola scriptura could be given than that seen in these statements of Cyril. He equates the teaching he is handing on to these catechumens with tradition, in which he specifically references 2 Thessalonians 2:15, that he says must be proven by Scripture. Tradition is simply the teaching of the church that he is passing on orally, but that tradition must be validated by the written Scriptures. He states further that the extent of authority vested in any teacher, be he bishop or layman, is limited to Scripture. No teaching is to be received that cannot be proven from Scripture. The church does have authority, as Cyril himself acknowledges, but it is an authority grounded in fidelity to Scripture and not principally in succession. According to Cyril, the church is subject to the final authority of Scripture, and even the church is to be disregarded if it moves outside that authority in its teaching.
http://www.christiantruth.com/articles/Testimony.html
I'm sure St. Cyril knew the complete verse:
2Thes:2:15: "Therefore, brethren, stand fast, and hold the traditions which ye have been taught, whether by word, or our epistle". (KJV)
“Tradition is simply the teaching of the church that he is passing on orally, but that tradition must be validated by the written Scriptures” —> yes, that is the standard. It must not contradict scripture. If anything contradicts scripture it should be junked.