All who rely upon obedience to Law are under a curse, for Scripture says--'Cursed is every one who does not abide by all that is written in the Book of the Law, and do it.'
Now it was to Abraham that the promises were made, 'and to his offspring.' It was not said 'to his offsprings,' as if many persons were meant, but the words were 'to thy offspring,' showing that one person was meant--and that was Christ.