What did Allāh mean by saying "I know what you know not"?

Imām Ibn al-Jawzī (d. 597/1201) summarized the scholars' opinions in his book "Zād al-Masīr" as follows:

1. "I know the rebellion and disobedience that is in the heart of Iblīs (Satan)." [Ibn ʿAbbās, Mujāhid, al-Suddī from his teachers]
2. "I know that from that offspring (human beings) there will be prophets and righteous people." [Qatādah]
3. "I know that I will fill Hell with jinn and mankind." [Ibn Zayd]
4. “I know the outcomes of affairs, so I test those whom you assume to be obedient, and trials lead them to disobedience—like Iblīs. And I test those whom you assume to be disobedient, and they obey.” [Al-Zajjāj]