וַיֹּ֤אמֶר לָהּ֙ מַלְאַ֣ךְ יְהוָ֔ה הַרְבָּ֥ה אַרְבֶּ֖ה אֶת־זַרְעֵ֑ךְ וְלֹ֥א יִסָּפֵ֖ר מֵרֹֽב׃
And the angel of the LORD said unto her: ‘I will greatly multiply thy seed, that it shall not be numbered for multitude.
Read halakhic rulings (Jewish law) on Genesis 16:10 from the Mishneh Torah and classical halakhic sources, free online.