Sheikh Muhammad al-Qannâs
A true dream may be seen be a non-Muslim.
This took place when the fellow prisoners of Joseph (peace be upon him) saw true dreams while they were in jail, and likewise when the king saw a good dream. All of these dreams were interpreted by Joseph (peace be upon him).
Such dreams, when seen by a non-Muslim, will not be part of prophecy.
Indeed, some narrations of the hadîth are worded as follows: “The Muslim’s dream is part of prophecy.”
The dream seen by an unbeliever or a liar will not be part of revelation or prophecy even if their dreams turn out to be true on occasion. Not everyone that tells truth is coming with something of prophecy. The soothsayer may speak a word of truth and the astrologer may accurately predict what will come to pass, although such things happen only rarely.
Al-Qurtubî writes, as quoted by Ibn Hajar in Fath al-Bârî (12/362):
The true and pious Muslim is the one whose state is suited to that of the Prophets, and that is why he is honored with something of which the Prophets were honored, and that is of having a glimpse of something of the unseen.
As for the unbeliever, the sinner, and the one whose good is mixed with bad, they are not so honored. If their dreams happen to come true sometimes, it will be considered in the same way that a liar sometimes speaks the truth. Not everyone who talks about the unseen will be relating something of prophecy; take for instance the soothsayer and the astrologer.
And Allah knows best.
Source: Islam Today