From another source with this url — http://explaining-the-catholic-faith.com/id49.html
I once undertook an experiment: I read from the entire New Testament at the rate of about 20 minutes per day. It took me about six weeks to complete. Jesus spent most of three years, nearly 24/7, with His Apostles. “[R]emember that for three years, night and day, I unceasingly admonished each of you. . . .” [John 20:31]. He obviously said much more to them than 20 minutes per day for six weeks. “There are also many other things that Jesus did, but if these were to be described individually, I do not think the whole world would contain the books that would be written.” [John 21:25]. So most of what He taught never got written down, but has been passed down to us by word of mouth, as Tradition. Jesus said, “Observe ALL that I have commanded.” This certainly includes everything Jesus taught, which is both in Scripture and outside Scripture. It would seem, logically, that these verses are enough to disprove Sola Scriptura. Matt 24:14 “This gospel of the kingdom shall be preached in the whole world as a testimony to all the nations, and then the end will come.” Many verses support this argument that Jesus taught many things that were never recorded in Scripture:
• Mark 4:2: He taught them many things by parables. . . .
• Luke 5:3: He got into one of the boats, the one belonging to Simon, and asked him to put out a little from shore. Then he sat down and taught the people from the boat. [It was not recorded what he taught them]
• Mark 4:33: With many similar parables Jesus spoke the word to them, as much as they could understand.
• John 4:40-42: When the Samaritans came to him, they invited him to stay with them; and he stayed there two days. Many more began to believe in him because of his word, and they said to the woman, “We no longer believe because of your word; for we have heard for ourselves, and we know that this is truly the savior of the world.” [Nothing is recorded regarding what Jesus taught to them during these two days.]
• Luke: 5:3: He got into one of the boats, the one belonging to Simon, and asked him to put out a little from shore. Then he sat down and taught the people from the boat.
• Mark 6:34: . . . He began to teach them many things. [none of these “many things” are recorded here.]
• John 16:12: I have yet many things to say to you, but you cannot bear them now. [These “many things” must have been spoken during Jesus’ post-Resurrection appearances; few of them are recorded.]
• John 20:30: Now Jesus did many other signs in the presence of the disciples, which are not written in this book.
• Acts 1:2-3: . . .the apostles. . . to them he presented himself alive after his passion by many proofs, appearing to them during forty days, and speaking of the kingdom of God. [These are not recorded in the Bible.]
St. Paul makes three statements arguing for the truth of Tradition: "So then, brethren, stand firm and hold to the traditions which were taught, whether by word or by letter from us." [2 Thess. 2:15] "Now we command you, brethren, in the name of our Lord Jesus Christ, that you keep aloof from every brother who leads an unruly life and not according to the tradition which you received from us." [2 Thess 3:6] "Now I praise you because you remember me in everything, and hold firmly to the traditions, just as I delivered them to you." [1Cor 11:2] Now, a Protestant argument goes like this: "The Bible does not tell us that there is a pool of Tradition which exists separately from the Bible. Nor does the Bible give to this alleged tradition the weight of added certainty of the revelation of God that is necessary for our Salvation or Sanctification or Service. When things of substance are spoken of in the Bible, the apostles appealed to the Written Word and not to an alleged outside source of tradition." [www.sxws.com]. First of all this argument is logically in error because Tradition, by its very nature, consists of a pool of beliefs. There is no need for the Bible to say there is a pool of tradition; it is self evident. Secondly, whenever statements are made about the Apostles appealing to Scripture, they are always appealing to the Old Testament. The New Testament had not yet been written. And the Jews had many traditions not found in the Old Testament. Finally, all arguments against Sacred Tradition fall flat in the face of Timothy 3:15.