כִּ֭י יִתְחַמֵּ֣ץ לְבָבִ֑י וְ֝כִלְיוֹתַ֗י אֶשְׁתּוֹנָֽן׃
Ainsi, quand mon cœur s’aigrissait et que mes reins étaient transpercés,
Rashi
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.”
Radak
When. Before I understood, my heart was filled with sourness in this matter, like the sourness of wine vinegar. In other words, I couldn't find anything sweet and pleasant in my heart to relieve me from the great distress.
Radak
and I was pricked in my reins. It is missing the letter "Bet" in the usage. He said, "And in my kidneys as well, which were advising and deliberating on this matter."