How do devils eavesdrop and inform soothsayers about the future when angels do not know the unseen? So how do devils eavesdrop on those who do not know what is in the future? And how is it that only Allah knows the unseen, yet He has given knowledge of it to the angel entrusted with writing down sustenance, lifespan, and deeds?

The unseen is of two types: absolute unseen, which only Allah knows. This is what creation cannot perceive, such as the knowledge of the Hour and the keys of the unseen. Quranic verses and Prophetic traditions have stipulated that the knowledge of the absolute unseen belongs to Allah alone. As for the relative unseen, some of creation, such as angels and messengers, may know it with Allah's permission and His informing them. Jinn may sometimes hear it by eavesdropping. This includes what Allah informs the angels about certain matters of the unseen after they have been decreed, such as some details of the fetus and the descent of rain after it has been commanded.