I have a question regarding 1 John 5:7-8 which reads in the KJV:
"For there are three that bear record in heaven, the Father, the Word, and the Holy Ghost: and these three are one. And there are three that bear witness in earth, the Spirit, and the water, and the blood: and these three agree in one."Is it true that these verses were inserted by Protestants in later centuries? Do old Coptic manuscripts of the Bible exist?
The whole New Testament is preserved in two dialects of the Coptic Language the Bohairic and the Sahidic with some whole books and fragments preserved in other dialects. Most of the historical and some of the literary Old Testament books in Bohairic are missing. Whereas much of these is preserved in Sahidic.
The only complete books of the Old Testament known to be extant in Bohairic are the Pentateuch, the Prophets with Lamentations, the Psalms, and Job. Of the others, we have fragments only, mostly taken from lectionaries.
The passage you are referring to in the first letter of St. John has been a source of controversy among scholars and is known as the 'Comma Johanneum'. The passage is absent from the manuscripts of the ancient Greek, Coptic, Syriac, Armenian, Ethiopic, Arabic, Slavonic versions but is found in the manuscripts of Latin Vulgate.
Some scholars claim that the Comma Johanneum is found only in eight late manuscripts, four of which have the words in a marginal note. Most of these manuscripts originate from the 16th century; the earliest manuscript, codex 221 (10th century), includes the reading in a marginal note which was added sometime after the original composition.
Some claim that the earliest instance of the passage being quoted as a part of the actual text of the Epistle is in a fourth century Latin treatise entitled Liber Apologeticus. Apparently the annotation arose when the original passage was understood to symbolize the Trinity (through the mention of three witnesses: the Spirit, the water, and the blood), an interpretation that may have been written first as a marginal note that afterwards found its way into the text.
However, St. Cyprian (Third Century) does show evidence of being familiar with these verses. In his De catholicae ecclesiae unitate 6, he says, "The Lord says, 'I and the Father are one'; and again it is written of the Father, and of the Son, and of the Holy Spirit, 'And these three are one.'" What is evident is that Cyprian's interpretation of 1 John 5:7 is that the three witnesses refer to the Trinity.
Our Church do accept these verses as authentic part of the first epistle of St. John.