Bruce Metzger, Textual Commentary of the Greek New Testament:

"Should the words O GEGONEN be joined with what goes before or with what follows? The oldest manuscripts (P66, P75, Aleph, A B ) have no punctuation here, and in any case the presence of punctuation in Greek manuscripts, as well as in versional and patristic sources, cannot be regarded as more than the reflection of current exegetical understanding of the meaning of the passage.

A majority of the Committee was impressed by the consensus of ante-Nicene writers (orthodox and heretical alike) who took O GEGONEN with what follows. When, however, in the fourth century Arians and the Macedonian heretics began to appeal to the passage to prove that the Holy Spirit is to be regarded as one of the created things, orthodox writers preferred to take O GEGONEN with the preceding sentence, thus removing the possibility of heretical use of the passage.

The punctuation adopted for the text is in accord with what a majority regarded as the rhythmical balance of the opening verses of the Prologue, where the climactic or 'staircase' parallelism' seems to demand that the end of the line should match the beginning of the next. (For discussion in support of taking O GEGONEN with what follows, see K. Aland, "Uber die Beduetung eines Punktes. (Eine Untersuchung zu Joh. 1, 3 4)." in Studies in the History and Text of the New Testament in Honor of Kenneth Willis Clark, ed. by Boyd L. Daniels and M. Jack Suggs (=Studies and Documents, XXIX; Salt Lake City, 1967), pp. 161 -187 (an expanded form of the study appeared in Zeitschrift fur die neutestamentliche Wissenschaft, LIX , pp. 174-209), and Ed. L. Miller, Salvation-History in the Prologue of John. The Significance of John 1:3/4 (Leiden, 1989), pp. 17-44."