Baruch Shem Kivod Malchuto IX: Lechem Rav
We recite “Blessed is the Name of His glorious kingdom for all eternity,” whenever we may have recited God’s Name in vain. We even recite this verse after reciting the blessing over the Tefillin shel Rosh because there are so many who believe that we should only recite one blessing.
The Chinuch (Mitzvah 30) explains that it is difficult for us to believe that we can cause any damage simply by reciting God’s Name in vain. We lose sight that it is our speech that came with the soul that God breathed into Man.
After we have made such an error, we repair the damage by declaring that we acknowledge the importance of God’s Name for we only “Know” Him through our perceptions, Appellations.
Jacob recited this sentence after his sons declared God’s Unity, because he sensed that although they made such a declaration, at least one was not totally committed to his words, otherwise, Jacob’s prophecy of the Redemption would have been restored.
Jacob felt that one of his children had spoken God’s Name in vain, and he therefore said this sentence. (Lechem Rav pages 310-311)
We should think as we recite this sentence that if our hearts were not totally committed to our declaration of God’s Unity in Shema, we can repair the damage by reciting this sentence.