1)
Why did he tell them "Lidrosh Es Hashem"?
1.
'Rashi': They should be unlike the 10 tribes, who seek only new gods and abandon the G-d of their fathers.
2.
Gra: Knowledge of Hashem should precede Avodah ? "Da Es Elokei Avicha v'Avdehu" (Divrei ha'Yamim I, 28:9). Then he veers from evil, and then he does good ("Sur me'Ra va'Aseh Tov" - Tehilim 34:15).
3.
Malbim: This refers to investigation; they are also commanded La'asos (action), [written] Torah and Mitzvah (oral Torah).
