Galatians 3:16

Now to Abraham and his seed were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ.

Now the promises were made to Abraham and his seed — Several promises were made to Abraham; but the chief of all, and which was several times repeated, was that of the blessing through Christ.

He — That is, God.

Saith not, And to seeds, as of many — As if the promise were made to several kinds of seed.

But as of one — That is, one kind of seed, one posterity, one kind of sons. And to all these the blessing belonged by promise.

Which is Christ — including all that believe in him. Genesis 22:18.