THE ANGEL AND THE BOOK
Revelation 10.1
The description of the angel in verse 1 is similar in certain ways to a description of Jesus Christ in some other visions. Is this the description of Christ or not, it is hard to tell, but this "strong angel" definitely stands very high in the hierarchy of power in the Kingdom of GOD.
Just like Jesus Christ has the Book and its unsealed seals, this angel has a little Book which he gave to John to eat. Very similar thing happened and to Jeremiah and Ezekiel (Jeremiah 15.16) (Ezekiel 3.1-3) (Revelation 10.9-10).
It can be also compared to expression, "writing on the hearts" in which the Law is placed in the soul of a person and a person became a Spiritual being possessed by GOD and lives his/her life only according to the Word of GOD.
~ Writing on the Hearts: (2Chronicles 30.12) (Psalm 40.7-8) (Proverbs 7.3) (Isaiah 44.3) (Jeremiah 24.7, 30.22, 31.33, 32.38.40) (Ezekiel 36.26-27, 39.29) (Zephaniah 3.9) (Hebrews 8.10, 10.16-17) (2Corinthians 3.3) (Hebrews 8.10, 10.16-17)
All holy men who received the Word of GOD all prophesied different prophesies. Here the angel of the Lord gave to John command to prophesy to the nations and the kings of the Earth (10).
How John fulfills this mission to prophesy to the nations and the kings is unknown, but one thing is absolutely certain that GOD made it happen.