Kommentar zu Tehillim 73:21

For my heart was in ferment Before I saw this downfall with the holy spirit, my heart was in ferment because the way of the wicked prospered, and my mind was on edge (אשתונן), an expression of a sharpened sword (שנון). When it is reflexive, the “tav” is placed in the middle of the radical, as is the case of every word whose radical commences with “shin.”