“You leave the commandment of God, and hold fast the tradition of men. … thus making void the word of God through your tradition which you hand on.”
Short answer
Jesus condemns the tradition of men that sets aside the commandment of God. The New Testament also commands Christians to hold to the traditions handed on by the apostles, by word of mouth as well as by letter. It uses the same Greek word in both places. The Church teaches that Sacred Tradition is this apostolic teaching, received from Christ and the Holy Spirit. It is distinct from customs that arose later, which can be changed.
Began from the project document Sacred Tradition in Scripture and was completed from primary sources. Every quotation is checked against the linked source.
Where this teaching appears on the Offshoots timelines: 1537, Scripture alone.
16 quotations in date order
“So then, brethren, stand firm and hold to the traditions which you were taught by us, either by word of mouth or by letter.”
“Now we command you, brethren, in the name of our Lord Jesus Christ, that you keep away from any brother who is living in idleness and not in accord with the tradition that you received from us.”
“I commend you because you remember me in everything and maintain the traditions even as I have delivered them to you. … For I received from the Lord what I also delivered to you, that the Lord Jesus on the night when he was betrayed took bread”
“Now I would remind you, brethren, in what terms I preached to you the gospel, which you received, in which you stand, by which you are saved, if you hold it fast—unless you believed in vain. For I delivered to you as of first importance what I also received, that Christ died for our sins in accordance with the scriptures”
“But as for you, continue in what you have learned and have firmly believed, knowing from whom you learned it and how from childhood you have been acquainted with the sacred writings which are able to instruct you for salvation through faith in Christ Jesus.”
“If, then, any one came, who had been a follower of the elders, I questioned him in regard to the words of the elders — what Andrew or what Peter said, or what was said by Philip, or by Thomas, or by James, or by John, or by Matthew, or by any other of the disciples of the Lord … For I did not think that what was to be gotten from the books would profit me as much as what came from the living and abiding voice.”
“Suppose there arise a dispute relative to some important question among us, should we not have recourse to the most ancient Churches with which the apostles held constant intercourse, and learn from them what is certain and clear in regard to the present question? For how should it be if the apostles themselves had not left us writings? Would it not be necessary, [in that case,] to follow the course of the tradition which they handed down to those to whom they did commit the Churches?”
“Now, what that was which they preached — in other words, what it was which Christ revealed to them — can, as I must here likewise prescribe, properly be proved in no other way than by those very churches which the apostles founded in person, by declaring the gospel to them directly themselves, both vivâ voce, as the phrase is, and subsequently by their epistles.”
“Of the beliefs and practices whether generally accepted or publicly enjoined which are preserved in the Church some we possess derived from written teaching; others we have received delivered to us in a mystery by the tradition of the apostles; and both of these in relation to true religion have the same force.”
“Hence it is manifest, that they did not deliver all things by Epistle, but many things also unwritten, and in like manner both the one and the other are worthy of credit. Therefore let us think the tradition of the Church also worthy of credit. It is a tradition, seek no farther.”
“If anyone rejects any written or unwritten tradition of the church, let him be anathema.”
“The Apostles, led by the inward instinct of the Holy Ghost, handed down to the churches certain instructions which they did not put in writing, but which have been ordained, in accordance with the observance of the Church as practiced by the faithful as time went on. Wherefore the Apostle says [2 Thessalonians 2:14]: "Stand fast; and hold the traditions which you have learned, whether by word"—that is by word of mouth—"or by our epistle"—that is by word put into writing.”
“…this truth and discipline are contained in the written books, and the unwritten traditions which, received by the Apostles from the mouth of Christ himself, or from the Apostles themselves, the Holy Ghost dictating, have come down even unto us, transmitted as it were from hand to hand”
“For Sacred Scripture is the word of God inasmuch as it is consigned to writing under the inspiration of the divine Spirit, while sacred tradition takes the word of God entrusted by Christ the Lord and the Holy Spirit to the Apostles, and hands it on to their successors in its full purity … Consequently it is not from Sacred Scripture alone that the Church draws her certainty about everything which has been revealed.”
“The Tradition here in question comes from the apostles and hands on what they received from Jesus' teaching and example and what they learned from the Holy Spirit. … Tradition is to be distinguished from the various theological, disciplinary, liturgical or devotional traditions, born in the local churches over time. … In the light of Tradition, these traditions can be retained, modified or even abandoned under the guidance of the Church's Magisterium.”