Acts 15:34 KJV
Notwithstanding it pleased Silas to abide there still
Acts 15:34 NASB
[But it seemed good to Silas to remain there.]
The New American Standard Bible has this verse between brackets, with a footnote that early manuscripts do not contain this verse.
The Revised Version doesn’t have this verse, but mentions it in a footnote.
The reason that this verse is omitted in different translations is, although this verse, or something similar to it, is quite old, it does not appear in the oldest manuscripts, and the manuscripts that do contain it are inconsistent about its text.
The verse as it appears in the KJV is found in less ancient Greek manuscripts (cursives, after the 9th century) and some other Italic, Syriac, Coptic, Armenian, Ethiopic, and other versions.
However some other, equally old resources, such as the C codex, and several cursives, change one word to make the verse read, “Notwithstanding it pleased Silas that they should abide there still.”
Several other sources, such as Codex D (Codex Bezae) and some Italic manuscripts, extend the verse with the ending, “and Judas traveled alone”; and a couple of Italic and Latin manuscripts add to that, “to Jerusalem.”
Erasmus annotated this verse with the comment that the reference to Judas did not appear in any Greek manuscript known to him.
As F.H.A. Scrivener put it, “No doubt this verse is an unauthorised addition, self-condemned indeed by its numerous variations. … [It must have begun as] a marginal gloss, designed to explain how … Silas was at hand in verse 40, conveniently for Saint Paul to choose him as a companion in travel.
This verse was omitted from the Revised Version and most modern versions, but many versions include it in a footnote.