“For the word of God is living and powerful, and sharper than any two-edged sword, piercing even to the division of soul and spirit, and of joints and marrow, and is a discerner of the thoughts and intents of the heart.” Fleshly human reasoning and spirit reasoning are at enmity with one another, and the sword of God’s word helps to distinguish between the two.
The joints and marrow are completely unseen, and yet God’s word can reach the deepest inner recesses of our thought process. This is something cannot be seen by others and often even ourselves. But when we allow Scripture to penetrate our mind, it will help us to assess our own intents and motivations. This cannot be done apart from the word of God.
Christ was the Word made flesh, and his tongue was a sharp sword. He may have used words that sometimes seemed harsh, but he knew what was in man and went straight to the heart. He addressed not those things that could be seen or heard superficially. Like all who Jesus encountered, Mary was not exempt from the piercings of this sword.