“Of the beliefs and practices whether generally accepted or publicly enjoined which are…”

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.

Basil of Caesarea · On the Holy Spirit (De Spiritu Sancto) · NPNF2 VIII, De Spiritu Sancto, Chapter XXVII, 66

The classic statement that a church may hold what no verse commands. Basil is defending a doxology — "with the Spirit" instead of "in the Spirit" — and the defence he reaches for is not a proof text but the practices nobody can find written down: signing with the cross, turning east to pray, the words said over the bread and the cup. His argument is that a Church which threw those out on the ground that they are unwritten would injure the Gospel in its vitals.