From John H. Leith’s Introduction to the Reformed Tradition:
Tradition and the gospel are indissolubly linked. Each is indispensable to the other and to the life of the Christian community. The gospel is God’s will “for us men, and for our salvation” as it has been worked out and disclosed in God’s revelation of himself, especially in the segment of history culminating in Jesus Christ and in the giving of the Holy Spirit at Pentecost. Tradition is the authoritative delivery of this gospel from believer to believer, from community to community, from generation to generation. Thus tradition has two uses. It may refer to the act of passing on, and it may refer to what is passed on. The New Testament speaks of the “faith which was once for all delivered to the saints” (Jude 1:3). This delivery is fundamentally God’s handing over of Jesus Christ (cf. Romans 8:31-32) “to share our existence and to effect our salvation.” It is secondarily the human act of authoritatively delivering this gospel to all people through the succeeding centuries. This secondary traditioning of the faith, this handing on of the gospel in an authoritative and living way, is essential to the life of the Christian community. Emil Brunner has put it very well:
Tradition is necessarily involved with the unique revelation of God in the historical facts concerning Jesus Christ. This unique historical event, in which the disclosure of salvation is contained, must be conveyed to later generations in order that they may share in its saving benefits. Paradosis, traditio belongs, therefore, to the very nature of the Gospel; to preach the Gospel means necessarily and always to transmit an account of what has happened for man’s salvation. Without tradition, no Gospel.