Matthew 3:9

And think not to say ... - They regarded it as sufficient righteousness that they were descended from so holy a man as Abraham. Compare John 8:33, John 8:53. John assured them that this was a matter of small consequence in the sight of God. Of the very stones of the Jordan he could raise up children to Abraham. The meaning seems to be this: God, from these stones, could more easily raise up those who should be worthy children of Abraham, or be like him, than simply, because you are descendants of Abraham, make you, who are proud and hypocritical, subjects of the Messiah’s kingdom. Or, in other words, mere nativity, or the privileges of birth, avail nothing where there is not righteousness of life. Some have supposed, however, that by these stones he meant the Roman soldiers, or the pagan, who might also have attended on his ministry; and that God could “of them” raise up children to Abraham.