Revelation 10:10 And I took the little book out of the angel’s hand, and ate it up; and it was in my mouth sweet as honey: and as soon as I had eaten it, my belly was bitter.

Even though it was predicted to John that it would be bitter, he is nevertheless obedient. He eats it, and it went as it was predicted to him: it was sweet, and bitterness followed. Thus the Lord would make the teachers obedient and willing in the time of the seventh trumpet. They would have sweetness in preaching, and bitterness because of that persecution. One is only able to proclaim the gospel and suffer on its account, if he has tasted its sweetness, and if he has eaten it, understands it, and feels the power of it in his heart.