The following contains excerpts from "To the Councilmen of All Cities in Germany That They Establish and Maintain Christian Schools" (1524), by Martin Luther.
See bold highlights for emphasis.
In proportion then as we value the gospel, let us zealously hold to the languages. For it was not without purpose that God caused his Scriptures to be set down in these two languages alone--the Old Testament in Hebrew, the New in Greek. Now if God did not despise them but chose them above all others for his word, then we too ought to honor them above all others…. And let us be sure of this: we will not long preserve the gospel without the languages. The languages are the sheath in which this sword of the Spirit is contained; they are the casket in which this jewel is enshrined; they are the vessel in which this wine is held; they are the larder in which this food is stored; and, as the gospel itself points out, they are the baskets in which are kept these loaves and fishes and fragments. If through our neglect we let the languages go (which God forbid!), we shall not only lose the gospel....
For this reason even the apostles themselves considered it necessary to set down the New Testament and hold it fast in the Greek language, doubtless in order to preserve it for us there safe and sound as in a sacred ark. For they foresaw all that was to come, and now has come to pass; they knew that if it was left exclusively to men's memory, wild and fearful disorder and confusion and a host of varied interpretations, fancies, and doctrines would arise in the Christian church, and that this could not be prevented and the simple folk protected unless the New Testament were set down with certainty in written language. Hence, it is inevitable that unless the languages remain, the gospel must finally perish….
Since it becomes Christians then to make good use of the Holy Scriptures as their one and only book and it is a sin and a shame not to know our own book or to understand the speech and words of our God, it is a still greater sin and loss that we do not study languages, especially in these days when God is offering and giving us men and books and every facility and inducement to this study, and desires his Bible to be an open book….
For this a knowledge of the language is needful above all else. The preacher or teacher can expound the Bible from beginning to end as he pleases, accurately or inaccurately, if there is no one there to judge whether he is doing it right or wrong. But in order to judge, one must have a knowledge of the languages; it cannot be done in any other way. Therefore, although faith and the gospel may indeed be proclaimed by simple preachers without a knowledge of languages, such preaching is flat and tame; people finally become weary and bored with it, and it falls to the ground. But where the preacher is versed in the languages, there is a freshness and vigor in his preaching, Scripture is treated in its entirety, and faith finds itself constantly renewed by a continual variety of words and illustrations.
We should not be led astray because some boast of the Spirit and consider Scripture of little worth, and others, such as the Waldensian Brethren think the languages are unnecessary....
So I can by no means commend the Waldensian Brethren for their neglect of the languages. For even though they may teach the truth, they inevitably often miss the true meaning of the text, and thus are neither equipped nor fit for defending the faith against error. Moreover, their teaching is so obscure and couched in such peculiar terms, differing from the language of Scripture, that I fear it is not or will not remain pure. For there is great danger in speaking of things of God in a different manner and in different terms than God himself employs. In short, they may lead saintly lives and teach sacred things among themselves, but so long as they remain without the languages they cannot but lack what all the rest lack, namely, the ability to treat Scripture with certainty and thoroughness and to be useful to other nations. Because they could do this, but will not, they have to figure out for themselves how they will answer for it to God.
Luther's Works, ed. W. Brandt and H. Lehman (Philadelphia Muhlenberg Press, 1962), 357-366.