One of the readings from the Christmas Eve service I attended last month was from Genesis 22. I noticed a small feature in verse 17 where God says to Abraham, "'I will surely bless you, and I will surely multiply your offspring as the stars of heaven and as the sand that is on the seashore.'"
Taken together, the images in these comparisons encompass a wide sweep (the stars above and the sand below), and this breadth mirrors the abundance of Abraham's offspring.