Extract and comments from earlier work: Revelation Chap. 10 V.1c
And I saw (a)another mighty angel coming down (b)from Heaven, clothed with a cloud: and (c)the rainbow upon his head, and his face was as it were (d)the sun, and his feet as pillars of (e)fire:
At this stage the 6th angel of the 7th seal has sounded, one woe is past, the second is in progress, and a third is yet to take place. The 3rd will not commence until the 7th angel sounds (Chp. 11:14-15).
(c) "The Rainbow"; AV. has "a", Comp. & Darby "the", which is correct. The other places in Scripture that a rainbow is mentioned is Rev. 4:3, which refers to Gen. 9:13, which is God's promise to Noah (Vs. 8-17) that He would never use water again to destroy the Earth's flesh.
In Rev. 4:3, we have sight of Jehovah God in Heaven with the symbol of His promise "round about the throne". Almighty God goes to great length in emphasising His integrity, in any promise or Covenant that He makes. The ones made in Holy Scripture all relate to Israel, with oblique reference to the "Nations", future blessings through Abraham, (Christ), (Isa. 60:3).
This whole Chapter relates to the later Covenants to Israel by Jehovah God, and to their near fulfilment. These relate to Jer. 31:31, and elsewhere, and are regarding the new Israel, the Nation in its ‘Promised Land’ borders, with a new heart, and with "peace and security"! (See: Ezek. Chps. 35-38).