The author of the Hiwar denies that the Messenger was aware of some unseen things, ignoring explicit Ayāt and sound Hadīths which al-Bukhārī and others related.  All of them explicitly state that Allāh Almighty can acquaint His Messengers with some unseen things.  The Almighty says in Sūrat al-Jinn, "He is Knower of the Unseen, and does not divulge His Unseen to anyone - except a Messenger with whom He is well pleased." (72:26-27) al-Qurtubī said in the tafsīr of the Ayah: 

Did Allāh acquaint His Messenger with some of the Unseen?
Shaykh `Abdul Hayy al-`Amrawī and Shaykh `Abdul Karīm Murād