Musar zu Bereschit 2:12

Concerning the example of the פטיש, hammer, used in the Tanchuma, the author of that story views the Torah like a hammer which when applied to a rock splits it and releases the kernel while the sparks produced burn the קליפות. This is why the author of the Tanchuma speaks about the son also being a smith. A smith is always busy applying the hammer to the anvil. Rabbi Levi chose the metaphor of the jeweler, goldsmith, since this is also a metaphor for Torah which described "gold as being found in a land called good" (Genesis 2,12). The land referred to is ארץ ישראל, and in no other country can Torah be studied as effectively as in ארץ ישראל (Bereshit Rabbah 16,4). The smith and the goldsmith therefore are metaphors describing the same thing. The forces of Esau will be burned by Jacob whose house will be a fire, as well as by the house of Joseph which will be like a flame.