Why do some versions have "Christ" in 1 Peter 3:15 while others have "God"?

Question

I'm finding inconsistencies between translations of 1 Peter 3:15

KJV

But sanctify the Lord God in your hearts...

NASB

but sanctify Christ as Lord in your hearts

ESV

but in your hearts honor Christ the Lord as holy...

I'm able to check the Strong's behind each of these using a free Android Bible app, and that's where I'm finding something different.

KJV

Sanctify [hagiazo] the Lord [kyrios] God [theos]

NASB

sanctify [hagiazo] Christ [Christos] as Lord [kyrios]

ESV Reads:

honor [hagiazo] Christ the Lord [theos kyrios]

Why are these differences here, and what are some resources that I can use to sort these out?

(Note: In asking about resources, I'm not asking an opinion based question- "What is the best resource" - this is an objective reference question- "What are some resources" Whether good or bad is not the issue, just something available)

Answer 1

The majority of manuscripts read (absent punctuation):

κύριον δὲ τὸν Θεὸν ἁγιάσατε ἐν ταῖς καρδίαις ὑμῶν

but many important early manuscripts read:

κύριον δὲ τὸν Χριστὸν ἁγιάσατε ἐν ταῖς καρδίαις ὑμῶν

These include the Bodner Papyrus (3rd/4th century), as well as all the principle Codices (Sinaiaticus, Alexandrinus, Vaticanus, Ephraemi). It is also represented this way in early Latin, Syriac and Coptic manuscripts, as well as in the commentary of Clement of Alexandria.

A commentary to the Nestle-Aland Critical Text mentioned in another answer reads:

In place of Χριστόν the Textus Receptus substitutes θεόν, with the later uncials (K L P) and most minuscules. The reading Χριστόν, however, is strongly supported by early and diversified external evidence (𝔓⁷² א A B C Ψ 33 614 1739 itar vg syr^p,h cop^sa,bo arm Clement), as well as by transcriptional probability, the more familiar expression (κύριον τὸν θεόν) replacing the less usual expression (κύριον τὸν Χριστόν).

The omission of τὸν Χριστόν in the patristic treatise de Promissionibus attributed to Quodvultdeus must be due to accidental oversight on the part of either translator or copyist.¹

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^{1 Metzger, B. M., United Bible Societies. (1994). A textual commentary on the Greek New Testament, second edition a companion volume to the United Bible Societies’ Greek New Testament (4th rev. ed.) (pp. 621–622). London; New York: United Bible Societies.}

Answer 2

You ask about the differences in the translations and you ask about resources.

The difference in translations is due to the underlying Greek text. The KJV is translated from the Received Text which is based (it is not exactly the same but it is based) on the Majority Text. This text dates from the 1550s. TR-Wikipedia

Most other translations are usually based on the Westcott and Hort text which gives very considerable weight to the Codex Sinaiticus and other early texts. This text dated from about 1880.

The best resource I know of to give a scholarly argument, based on massive achievement in the science of textual analysis is :

Dean Burgon 'Revisions Revised'. There is a kindle edition available on Amazon.

I read this book as a teenager in about 1969 and I have never departed from what I learned between its pages.