The New John Gill Exposition of the Entire Bible1 Corinthians 16:21
The salutation of me Paul with mine own hand.
] The apostle
had an "amanuensis", that wrote the epistle for him; but to prevent
counterfeits, and that the church to whom he wrote might be assured
of the genuineness of the epistle, that it was truly his own, he
wrote with his own hand his common salutation; see (2 Thessalonians 3:17,18) ,
and which is not in the following words, but what is expressed in
(1 Corinthians 16:23) .