"The prayers prescribed or approved for universal use in public worship cannot be opposed to any revealed truth. Hence the axiom, Lex orandi est lex credendi,--the rule of prayer is the rule of faith."
The following is taken from Sylvester Berry, D.D., The Church of Christ (1927), Ch. XVI: "The Extent of Infallibility," pp. 503-9 (available from the ITOPL collection).