Charles Ellicott Commentary Genesis 24:60

"And they blessed Rebekah, and said unto her, Our sister, be thou [the mother] of thousands of ten thousands, and let thy seed possess the gate of those that hate them." — Genesis 24:60 (ASV)

Thousands of millions. —Hebrew: thousands of ten thousands. A million was a number which at this early period the Hebrews had no means of expressing. The blessing contains two parts: the first, the hope of fruitfulness founded on the primeval command (Genesis 1:28); the second, that of victory in war .