Sometimes anti-perfect preservationists, opponents of the perfectly preserved Word in the Hebrew and Greek Textus Receptus, argue that the presence of the kethiv / qere in the Hebrew Old Testament proves that Scripture has not been perfectly preserved. While this is not the easiest issue to address for someone who does not know Hebrew, the Christian who accepts God's promises of preservation (Psalm 12:6-7; Isaiah 59:21; Matthew 28:19-20; Revelation 22:18-19, etc.) should have an answer to people who attempt to cast doubt on God's promises to keep His Words from the presence of the kethiv / qere.
In the Hebrew text, the kethiv / qere are notes indicating that a given word is written (kethiv) one way but is to be read (qere) a different way. Anti-preservationists typically assert that the kethiv / qere are textual variants, similar to the footnotes in a NA27 or UBS5 Greek NT. The vast majority of the time this is simply assumed, not proven. However, anti-preservationists must justify this assumption. Why is there always only one qere / kethiv pair if the qere is a textual variant? Were there never, ever multiple variants?
Anti-preservationists must also prove that the traditional Jewish view of the kethiv / qere is incorrect (see my essay Evidences for the Inspiration of the Hebrew Vowel Points for sources):
The Talmud clearly speaks of the Kethiv/Qere distinction and other textual distinctions considered Masoretic, and traces them to Moses at Sinai.
Said R. Isaac, “The correct text of Scripture deriving from the scribes, the embellishments of the letters derived from the scribes, the words that are read in the text not as they are spelled out, the words that are spelled out but not read—all represent law revealed by God to Moses at Sinai.”
“The correct text of Scripture deriving from the scribes”: These are the words in Hebrew for land, heaven, Egypt [where the tone vowels are lengthened, but nothing in the lettering indicates this change].
Up until quite recently the Kethiv/Qere were “by all writers, allowed to be, at the least, nearly as old as the Times of Ezra; and by many of the ancient Jewish Writers they are taken to be as old, as the Text, to which they belong” (pg. 286, Whitfield, A Dissertation on the Hebrew Vowel-Points).
Note as well that a variety of explanations can be made by for the kethiv / qere by advocates of perfect preservation other than (alleged) corruption in the Hebrew text by following the standard harmonizing practice of old Jewish interpreters such as Kimchi, to explain the existence of both readings. For example, Whitfield explains the three instances in Psalm 71:20 of the same kethiv / qere by writing: “I cannot think it probable, three Mistakes of the same kind could, any how happen in the Compass of one Verse. Supposing the points as ancient as we are endeavouring to prove them, I believe this Diversity in this, and some other places, betwixt the reading by the Letters and by the points, was originally designed by the Holy Penman, perhaps to shew that the Import of the place might be applied to himself as a single Person, or to the Community whereof he was the Head” (pg. 198, A Dissertation on the Hebrew Vowel-Points).
There are "things hard to be understood" in the kethiv / qere, and no one explanation (including the modern anti-preservation one) easily explains all the data. I believe a perfect preservationist would do well to take seriously the traditional Jewish view that both readings were present from the time Moses gave the law at Sinai, although I think it is also possible that (under inspiration, as for the book of Ezra itself, etc.) Ezra could have put at least some of them in because, perhaps, of pronunciation changes over time. After all, Ezra is about 1,000 years after Moses and pronunciation can change in 1,000 years very, very easily. Why could not (for example) the kethiv / qere ("to him," English) in Job 13:15 have represented a way to convey the idea of "to him" in Hebrew in the time in which Job (as I believe) penned the book of Job (the kethiv) but by the times of Ezra the qere have represented the way to convey this same idea, and so both accurately be represented in the KJV translation?
Jews and Christians have been aware of the kethiv / qere in the Hebrew Old Testament for millennia without adopting the modern notion that their presence indicates a failure on God's part to preserve His Words or the presence of corruption in the text. There is no need whatsoever to abandon traditional explanations for their presence and reject the plain meaning of texts on verbal, plenary preservation because of their presence.
Please see my essays The Battle Over the Inspiration of the Hebrew Vowel Points and Evidences for the Inspiration of the Hebrew Vowel Points for more information. (Note: material in these essays, especially the second one, can get technical and difficult to follow unless one knows Hebrew.)