Our two oldest witnesses to the Greek text of Paul support this reading: the Chester Beatty Papyrus of Paul (P46) from around AD 200; and Vaticanus from the fourth century. This early Alexandrian textual tradition is supported in a strong group of 'Western' witnesses (D G it etc.).
P46, the earliest evidence for the reading QEOU KAI XRISTOU in Gal 2.20.
Some account of the slender argumentative basis behind the general consensus of contemporary scholarship can be seen in the arguments summarised in Metzger's Textual Commentary:
- God and Christ ‘can scarcely be regarded as original since Paul nowhere else expressly speaks of God as the object of a Christian’s faith’ (p. 524).
- ‘the son of God’ best explains the origin of the other readings:
- ‘It is probable that in copying, the eye of the scribe passed immediately from the first to the second TOU, so that only TOU QEOU was written (as in ms. 330); since what followed was now incongruous, copyists either added TOU UIOU or inserted KAI XRISTOU.’ (p. 524)
- Romans 4!!
- Metzger's argument involves an imaginary process, a crucial part of which is found only in a single twelfth-century manuscript. It doesn’t explain what may have drawn a scribe to add ‘and Christ’, although it does seem to acknowledge that this was a very early variant.
- It is really a desperate measure because as is universally admitted the ‘Son of God’ reading is a smooth reading, making perfect sense and generally consistent with Pauline thought. If one asks what sort of reading scribes would have preferred clearly the answer is precisely this sort of reading.
- Here the more difficult reading seems pretty clear and it has very good external attestation.
So what Paul wrote was obviously (!): 'The life I now live in the flesh, I live by faith in God and Christ who loved me and gave himself over for me.'