Hello,
In many, many, many places. Here are just a couple:
1 Thessalonians 3:10 - Night and day more abundantly praying that we may see your face, and may accomplish those things that are wanting to your faith? (why are the Scriptures not enough?)
1 Thessalonians 2:14 - Therefore, brethren, stand fast; and hold the traditions which you have learned, whether by word, or by our epistle. [emphasis mine]
2 Peter 3:16 - As also in all [Paul’s] epistles, speaking in them of these things; in which are certain things hard to be understood, which the unlearned and unstable wrest, as they do also the other scriptures, to their own destruction. (how can something self-attesting and revealing be able to be so easily misinterpreted? if we are warned about misinterpreting Scriptures, there must be something outside of them to be able to interpret them properly)
Colossians 4:16 - And when this epistle shall have been read with you, cause that it be read also in the church of the Laodiceans: and that you read that which is of the Laodiceans. (one of many places where a non-canonical source is appealed to - what need of this if all is contained in the canonical Scriptures?)
Ephesians 1:13 - In whom you also, after you had heard the word of truth, (the gospel of your salvation; ) in whom also believing, you were signed with the holy Spirit of promise (one of many places we are told that Faith comes by hearing, not reading)
2 Timothy 1:13-14 - Hold the form of sound words, which thou hast heard of me in faith, and in the love which is in Christ Jesus. Keep the good thing committed to thy trust by the Holy Ghost, who dwelleth in us. (that which is transmitted orally - Sacred Tradition - is protected by the Holy Spirit)
This is just a brief sampling.