'Seed' in the Bible

Neither are they all children because they are Abraham’s descendants. On the contrary, your offspring will be traced through Isaac.

That is, it is not the children by physical descent who are God’s children, but the children of the promise are considered to be the offspring.

And just as Isaiah predicted:If the Lord of Hosts had not left us offspring,we would have become like Sodom,and we would have been made like Gomorrah.