Holy Scripture is the main source of our knowledge about God in general and about Christ in particular. Yet Scripture can be understood and interpreted in various ways; indeed, all heresies have been underpinned by references to Scripture and quotations from the Bible. It is therefore essential to find some criteria for a correct understanding of the Bible. For the Church the criterion is Holy Tradition, of which Scripture is a part. Tradition compromises the centuries-old experience and life of the Church, reflected not only in Scripture but also in the acts and definitions of faith of the Ecumenical Councils, in the works of the Church Fathers and in liturgical worship.

Tradition is not merely a supplement to Scripture; it bears testimony to the permanent and living presence of Christ in the Church. The authors of the New Testament books emphasize that they are 'witnesses': 'That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked upon and touched with our hands, concerning the word of life-the life was made manifest, and we saw it, and testify to it, and proclaim to you the eternal life which was with the Father and was made manifest to us' (1 John 1.1-2). Yet Christ continues to live in the Church, and the experience of contact with him, of life in him, engenders a new witness which is fixed in Tradition. 

-Metropolitan Hilarion Alfeyev