God made promises to Abraham (Gen.12:1-3, 17:7) & his’ Descendant/The Seed‘ (Christ, the Messiah was coming from Abraham’s lineage), but the Jews stumbled on this (Isaiah 28:16, Rom. 9:33), they misinterpreted it & took it the blessings were just for all Abraham’s descendants in the flesh, Israelites. Sadly many Jews still believe that today!
In the Old Testament the Hebrew word H2233 Zera, = “seed” is a singular noun that can also mean offspring. Many modern bibles translate or change the Hebrew word “seed” as “descendants,” “children,” (plural only). This makes it even more difficult to understand, altering the scriptures & the doctrine. To know if ‘seed’ has singular or plural meaning we need to read in context. In Greek there are distinct words for seed (spermati) & seeds (spermasin).