Genesis 21:12

Isaac . . . thy seed. Here ser'a is in the sing sense, because of the word "Isaac", and because of the sing verb "it shall be called. " Zer'a is a collective noun (like Eng. "sheep"), but the context must determine whether it is sing, or plural. It is to this verse Galatians 1:3 , Galatians 1:16 refers; not to Genesis 12:7 , where it is indefinite; or Genesis 17:7 where the verb and pronouns show it is plural. See note there, and on Galatians 1:3 , Galatians 1:16 ; and compare Romans 9:7 . Hebrews 11:18 . "Thy seed" is therefore "Christ". The difference of the 30 years comes in here: 430 to the Exodus ( Gen 12:40 ) from Genesis 12:4 , when Abraham was 75: 25 thence to Isaac's birth: and now, 5 to his recognition as the seed = 30 years.