Allah doesn't speak to any human, except by unique circumstances

Allah doesn't speak to any human, except by unique circumstances

"It is not given to any human being that Allah 
should speak to him unless (it be) by revelation, or 
from behind a veil, or (that) He sends a Messenger 
to reveal what He wills by His leave. Verily, He is 
Most High, Most Wise." (42:51)

"It is not given to any human being that Allah should 
speak to him unless (it be) by revelation,"

This refers to how Allah sends revelation.
Sometimes He casts something into the heart of
the Prophet, and he has no doubt that it is from
Allah,

As it was reported in Sahih Ibn Hibban that
the Messenger of Allah said:

"Ar-Ruh Al-Qudus (i.e., Jibril) breathed into my heart that no soul will die until its allotted provision and time have expired, so have Taqwa of Allah and keep seeking in a good (and lawful) way."

"or from behind a veil" --

as He spoke to Musa, peace be upon him. He
asked to see Him after He had spoken to him, but
this was not granted to him.

"or (that) He sends a Messenger to reveal what He wills
by His leave."

as Jibril, peace be upon him, and other angels
came down to the Prophets, peace be upon them.