Why does it say "ha'Lo Yochi'ach"?
Rashi: He will afflict you for this!
Radak: You think that He will not afflict You for your deeds. It is accepted, generation after generation, that He afflicts nations for their evil! He brought the flood and destroyed all flesh due to their evil deeds, and rained fire and sulfur on Sedom and destroyed their land due to their evil. He saw and knew their deeds and punished according to their evil. How can you say that He does not see and hear people's deeds?
Malbim: Since he refutes nations, his rebuttal will be revealed either via an individual that he teaches, e.g. specially qualified individuals - Chachamim or Nevi'im - and teaches to them His Hashgachah, or via afflicting great nations, until via this, they recognize His Hashgachah, reward and punishment. This is like the signs he did in Egypt and several countries to inform His Hashgachah. So Hashem proves that He knows not only their deeds, rather, even their thoughts and follies. Nothing is hidden from Him!
Why does it mention that he teaches Da'as to people?
Radak: Given this, how can he not know their Da'as and thoughts? He taught them!
