The Codex Alexandrinus, designated by the siglum A or 02, δ 4, is a manuscript of the Greek Bible, written on parchment. Using the study of comparative writing styles (palaeography), it has been dated to the fifth century. It contains the majority of the Greek Old Testament and the Greek New Testament. It is one of the four Great uncial codices. Along with Codex Sinaiticus and Vaticanus, it is one of the earliest and most complete manuscripts of the Bible.

The Codex Sinaiticus, designated by siglum א‎ [Aleph] or 01, δ 2, also called Sinai Bible, is a fourth-century Christian manuscript of a Greek Bible, containing the majority of the Greek Old Testament, including the deuterocanonical books, and the Greek New Testament, with both the Epistle of Barnabas and the Shepherd of Hermas included. It is written in uncial letters on parchment. It is one of the four great uncial codices. Along with Codex Alexandrinus and Codex Vaticanus, it is one of the earliest and most complete manuscripts of the Bible, and contains the oldest complete copy of the New Testament. It is a historical treasure, and using the study of comparative writing styles (palaeography), it has been dated to the mid-fourth century.