Adam Clarke on Revelation 14:1

A Lamb stood on the mount Sion - This represents Jesus Christ in his sacrificial office; mount Sion was a type of the Christian Church.

And with him a hundred forty and four thousand - Representing those who were converted to Christianity from among the Jews. See Rev 7:4.

His Father's name written in their foreheads - They were professedly, openly, and practically, the children of God, by faith in Christ Jesus. Different sects of idolaters have the peculiar mark of their god on their foreheads. This is practised in the east to the present day, and the mark is called the sectarial mark. Between eighty and ninety different figures are found on the foreheads of different Hindoo deities and their followers.

Almost every MS. of importance, as well as most of the versions and many of the fathers, read this clause thus: Having His Name and his Father's name written upon their foreheads. This is undoubtedly the true reading, and is properly received by Griesbach into the text.