Nehemiah 7:68, is missing from most Hebrew manuscripts. This fact suggests it was not in the autograph (original). Nevertheless, it is included in most English translations:
67 besides their male and female servants, of whom there were 7,337. And they had 245 singers, male and female. 68 Their horses were 736, their mules 245,[a] (Nehemiah 7:67-68)
a. Nehemiah 7:68 Compare Ezra 2:66 and the margins of some Hebrew manuscripts; Hebrew lacks Their horses… 245
The ESV notes, similar text is found in Ezra 2:66 and in the margins of some manuscripts. The correctness of the text is not in question. Its presence as authentic to Nehemiah is in doubt.
For reference, here are the same verses in Ezra:
65 besides their male and female servants, of whom there were 7,337, and they had 200 male and female singers. 66 Their horses were 736, their mules were 245, (Ezra 2:65-66)
The missing Nehemiah verse is likely due to a scribal error of a type known as parablepsis which is caused when "a scribe miscopies text due to inadvertently looking to the side while copying, or accidentally skips over some of it..." A specific type of parablepsis involves two lines of verse which end with words having the same ending and is known as homeoteleuton:
In the field of palaeography and textual criticism, homeoteleuton has also come to mean a form of copyist error present in ancient texts. A scribe would be writing out a new copy of a frequently reproduced book, such as the Bible. As the scribe was reading the original text, his eyes would skip from one word to the same word on a later line, leaving out a line or two in the transcription. When transcripts were made of the scribe's flawed copy (and not the original) errors are passed on into posterity
It is easy to use homeoteleuton when making a copy of Nehemiah to explain the missing verse:
The scribe inadvertently skipped over verse 68 which has the same word ending as verse 67 and produced a copy which lacked the verse, an error which was continued in future copies.
In addition to homeoteleuton when making a copy, it is also possible to use parablepsis and place this error in the making of the autograph of Nehemiah:
In his answer to a question over a mathematical contradiction, Dɑvïd asserts parablepsis occurred in the making of Nehemiah. The scribe was copying from Ezra and skipped from the end of 2:65 to near the end of 2:66 and the autograph of Nehemiah lacked the verse.
Obviously making an original (or copy of) Nehemiah using Ezra would be atypical; yet parablepsis from Ezra would account for the absence of 7:67 from most manuscripts. On the other hand, making a copy of Nehemiah would be common and placing a homeoteleuton mistake when copying from the original Nehemiah (or an early copy) which had the verse would also explain why it is missing from most manuscripts.
What factors other than the scribal errors of homeoteleuton or parablepsis attest to the authenticity, or lack thereof, to Nehemiah 7:68?