Parshat Lech L'Cha
In perek 16 we find Hagar running away from Sarai's house after being oppressed. She runs into the desert and ends up having a dialogue with an angel. In 16:9 it says, one of a number of times, "And the angel of Hashem said to her..."
Rashi points out that every time something was said, the angel was replaced by different angel and that is why every statement is preceded by "The angel said" - because each statement was a different angel.
Question: Why? For what purpose did the angel have to be swicthed for every sentence? Why couild one angel not conduct the entire dialogue?