Licking the glue of an envelope with the tongue while fasting.
Moistening the glue of an envelope with one's tongue in the state of fasting is disliked (Makruh), because there is taste in the glue, and tasting the flavor of anything in the state of fasting is disliked (Makruh); however, if one takes saliva on the finger and moistens the glue with it, there is no harm in it. (Aham Masail/Vol:4/Page:94)