Hisgalus 10:9-10

And I went to the malach, telling him to give me the sefer katan (small book) and he says to me, Take and eat it, and it will make your stomach bitter, but in your mouth it will be sweet as devash (honey). And I took the sefer katan out of the hand of the malach and ate it, and it was in my mouth as sweet as devash (honey), but, when I ate, my stomach was made bitter.