‘The Holy Spirit by Whom believers should be God-taught does not render the Scriptures less necessary. He is not given to us in order to introduce new revelations, but to impress the written Word on our hearts; so that here the Word must never be separated from the Spirit. The former works objectively, the latter efficiently; the former strikes our ears from without, the latter opens the heart within. The Spirit is the teacher; Scripture is the doctrine which He teaches us.'
Francis Turretin, Institutes of Elenctic Theology, Vol I, p.59