Mark 11:26 KJV
But if ye do not forgive, neither will your Father which is in heaven forgive your trespasses.
The New American Standard Bible has this verse between brackets and the footnote that early manuscripts do not contain this verse
Mark 11:26 NASB
[ But if you do not forgive, neither will your Father who is in heaven forgive your transgressions.” ]
The Revised Version omits this verse, but has a footnote saying: “Many authorities add verse 26” followed by the text of the verse.
The reason for putting this verse between brackets, or omitting it completely is found in the fact that early manuscripts, and most later manuscripts do not contain this verse, and maybe because this verse is very similar to Matthew 6:15.
This verse appeared in the Complutensian Polyglot and most Textus Receptus editions, but Erasmus omitted it, and noted that it was missing from ‘most’ Greek manuscripts.
The verse is not in different manuscripts, and some Italic, Vulgate, Syriac, and Coptic manuscripts, and the Armenian and Georgian versions.
The UBS edition gave the omission of this verse a confidence rating of A.