From Textus Receptus
Hebrews 1:3 Who being the brightness of his glory, and the express image of his person, and upholding all things by the word of his power, when he had by himself purged our sins, sat down on the right hand of the Majesty on high;
The complaint of a scribe, written in the margin of Codex Vaticanus at Hebrews 1:3 says:
αμαθεστατε και κακε, αφες τον παλαιον, μη μεταποιει (Fool and knave, can't you leave the old reading alone and not alter it!)
The NIV reads: After he had provided purification for sins he sat down on the right hand of the Majesty in heaven. omitting "by himself"
The NASB reads: When He had made purification of sins, He sat down at the right hand of the Majesty on high. omitting "by himself"