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But in the Torah of God is his will, and in his Torah he shall meditate day and night.

Rashi

But in the Torah of God is his will

Here you learn that the seat of the insulters brings him to the wasting of Torah.

And in his Torah he shall meditate

In the beginning it is called the Torah of God; and from when he toiled in it, it is called his Torah.

He shall meditate

Every language of hegeh (meditation) is in the heart; like you say: (Psalm 19:14) and the meditation of my heart...

Ibn Ezra

And in his Torah he shall meditate

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