Oldest Bible Source
Only Goes Back 4th Century?

Codex Sinaiticus
Sometime in the Middle Fourth Century (300s) C.E.

Although this manuscript is usually considered among the Alexandrian family of witnesses, in the Gospel of John (1:1-8:38), it is regarded as transmitting a Western Text.  Codex Sinaiticus was originally a complete Bible. The NT portion (148 leaves) is well preserved and includes the Letter of Barnabas and the Shepherd of Hermas.

Although this manuscript is usually considered among the Alexandrian family of witnesses, in the
Gospel of John [1:1-8:38], it is regarded as transmitting a Western Text.

The leaves (pages) in the Codex Sinaiticus measure 15"x14". The letters were written in a brown ink, four columns per page, with 48 lines to a column, and usually 12-16 letters perline.

The text is written on the ruled lines in scriptio continua with some punctuation (high and middle points and colon). Some letters are crowded in a smaller size at the end of a line. Often, sections of text end in mid-line; a new section begins at the beginning of the next line and is moved into the margin slightly.

Scholars have identified three scribes as having produced the manuscript.

Scribe A worked on New Testament
The one who was involved with the NT is labeled Scribe A.

Old Testament Copied from Dication (oral reciting similar to Quran)
It can be shown that the scribe of the OT copied the manuscript from dictation in part of that portion.

New Testament Copied from Exemplar
Likewise, it is held that the NT portion was copied down from a written exemplar.

9 Correctors From 380s to 1100s C.E.
Taken altogether, perhaps as many as nine correctors worked on the manuscript from the fourth to the twelfth century.

The Gospel of John begins at the top of the left column. Notice the way in which a new section is treated in the manuscript.

In line nine of column one, notice that a letter epsilon (e) has been placed between the delta (D) and epsilon (E). Note arrow 1 to see the precise position. At the end of the line, one can see a faint high point that probably was also inserted later (arrow 2). Certainly the mid point in the next line (line 2 below) was squeezed in by the later corrector (arrow 3).

What we can conclude is that originally the text had the same reading as Papyrus 66. The corrector, however, has adapted the text resulting in the same reading as the corrected text of Papyrus 75 and the text of Codex Vaticanus.