The heavenly voice told John to take the open scroll from the angel and eat it. When he had eaten it, he was commanded by God to prophesy again about all people.

Revelation 10:8-11

8 The one whose voice I had heard from heaven spoke to me again. He said, “Go and take the open scroll from the hand of the angel who is standing on the ocean and on the land.” 9 So I went to the angel and asked him to give me the little scroll. He said to me, “Take it and eat it. In your mouth it will taste sweet like honey, but it will make your stomach bitter.” 10 I took the little scroll from the angel’s hand and ate it. In my mouth it tasted sweet like honey, but when I had eaten it, it made my stomach turn sour. 11 The one whose voice spoke from heaven said to me, “You must ◄prophesy again/proclaim again what I will reveal to you► about many people-groups, many nations, speakers of many languages [MTY], and many kings.”