What is the meaning of "Yischametz"?
Radak: It is an expression of "Chometz Yayin" (Bamidbar 6:3, i.e. vinegar). I.e. before I understood this, I did not find a sweet, pleasant matter in my heart to have tranquility from this great confusion.
Malbim: At the time when I purified my heart and thoughts.
What is "[v'Chilyosai] Eshtonan"?
Rashi: It is an expression of Cherev Shinun (a sharp sword). Any word whose root begins with Shin receives a Tov in Hispa'el conjugation.
Radak: The prefix Beis is omitted (it is as if it says uv'Chilyosai), like "ha'Nimtza Veis Hashem" (Melachim II, 12:11) and similar verses. Also in my kidneys, which counsel, I was very sharp about these matters.
Malbim: My kidneys sought the correct counsel.
