The first angel's message is the "everlasting gospel", namely the "good news of God's infinite love".

The three angels of mercy, including the preacher of the everlasting gospel, were close by as well.

What is the everlasting gospel that these messengers proclaim?

The introduction to the book asserts that it "contains, as does the Bible, the fullness of the everlasting gospel.

Here are the last fourteen lines of William Blake's "The Everlasting Gospel":

She also preached at her own Everlasting Gospel Mission, a small whitewashed room decorated with her vivid paintings, where she died in 1980.

It is used in a rather different sense in William Blake's poem The Everlasting Gospel:

W. Blake, "The Everlasting Gospel," 2a and g. 24.

Time an Apparition of Eternity and Voice of the Everlasting Gospel, (1791-2)

Suddenly standing behind Jesus were five heavenly beings, three of whom she recognized: Christopher, the angel with the everlasting gospel; Caleb; and Nahum.