What is the significance of "Da Es Elokei Avicha v'Avdehu"?
Radak: This is like "v'Yadata Es Hashem Elokecha." He said Elokei Avicha - rely on tradition until you yourself know.
Metzudas David: Investigate with your intellect to know Him. If your intellect does not suffice, do not abandon Him. He is Elokei Avicha - rely on tradition. A father helps his son reach the truth!
Malbim: Hashem did great Chasadim with you - this increases your obligation. Do not rely on tradition for Emunah and mindsets. Investigate His ways to reach deeper understanding of Him, and serve Him constantly.
What is "b'Lev Shalem uv'Nefesh Chafetzah"?
'Rashi': It does not say Levav Shalem, which would imply two hearts. Rather, have only one heart. "V'Hayah Levavchem Shalem Im Hashem" - it says Shalem (singular), for your two hearts should be like one. It says "v'Sa'adu Libechem", not Levavchem, for angels have only one heart (Bereishis Rabah 48:11).
Malbim: Do not have other motivations for serving Him. Rather, your heart should be complete with Him. Do not serve amidst compulsion and fear of punishment, rather, amidst love - your soul should desire serving Him! Then, the heart will arouse only images of Avodas Hashem. He will not desire evil at all, and not need to conquer the Yetzer.
Why does it say "Ki Kol Levavos Doresh Hashem"?
'Rashi': Here it properly says Levavos (plural) - He investigates both good and evil hearts.
Malbim: The heart rules over the Nefesh.
Why does it add "v'Chol Yetzer Machashavos Mevin"?
'Rashi' citing Bereishis Rabah 89:3: Before man is created, Hashem knows what he will think.
Radak: The action of the heart is called Yetzer. It forms thoughts, for good or bad.
Malbim: Man thinks many thoughts. The Nefesh arouses many images - most are evil, e.g. lust, pride, anger... Then, one must fight with the Yetzer ha'Ra. Hashem investigates which way the heart decides, and also the thoughts that cross the heart.
What is the significance of "Im Tidreshenu Yimatzei Lach"?
'Rashi': This is why I told you "v'Dirshu Kol Mitzvos Hashem" (the previous verse)!
Malbim: Then you will know Elokei Avicha, and how to serve Him - one who wants to be Metaher himself, Hashem helps him (Shabbos 104a).
What do we learn from "Yaznichacha La'ad"?
'Rashi': It does not say Ya'azavcha, rather, Yaznichacha, which is harsher - "v'He'eznichehu", "Zanach Hashem Mizbecho." Malbim - Zanach is making an impression on something far from him.
