Jewish History: Biblical History: David's Five Pebbles:
Why did David take five pebbles with him when he went to fight Goliath?
The Midrash says that the five pebbles corresponded to Abraham, Isaac, Jacob, Aaron (because Goliath had killed the two sons of the high priest Eli), and G-d Himself. The Midrash further says that the stones were competing for the privilege of being thrown at Goliath. Aaron's stone claimed the right of vengeance because Goliath had killed Eli's sons; the patriarchs' stones claimed it because Goliath was mocking the Hebrews, their descendants; and G-d's stone claimed it because Goliath was mocking G-d. The dispute was settled by the five stones merging into a single stone.
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