Ambrose of Milan
Catena Aurea · Lukasevangelium 3
Then said he to the multitude that came forth to be baptized of him, O generation of vipers, who hath warned you to flee from the wrath to come? Bring forth therefore fruits worthy of repentance, and begin not to say within yourselves, We have Abraham to our father: for I say unto you, That God is able of these stones to raise up children unto Abraham. And now also the axe is laid unto the root of the trees: every tree therefore which bringeth not forth good fruit is hewn down, and cast into the fire,
But although God can alter and change the most diverse natures, yet in my mind a mystery is of more avail than a miracle. For what else than stones were they who bowed down to stones, like indeed to them who made them. It is prophesied therefore that faith shall be poured into the stony hearts of the Gentiles, and through faith the oracles promise that Abraham shall have sons. But that you may know who are the men compared to stones, he has also compared men to trees, adding, For now the axe is laid to the root of the tree. This change of figure was made, that by means of comparison might be understood to have now commenced a more kindly growth of manhood.