Charles Ellicott Commentary Genesis 16:10

"And the angel of Jehovah said unto her, I will greatly multiply thy seed, that it shall not be numbered for multitude." — Genesis 16:10 (ASV)

I will multiply your seed. We have here the purpose of the Divine manifestation. Abram’s son must not be mixed up with and lost among the debased population of Egypt, but must be the father of a free people; and Hagar will now submit to her lot as a slave, that she may secure liberty for her offspring.