There are biblical examples of God speaking to a person through a dream. I have always considered this a possibility, since a sleeping person may have inwardly slowed down enough to be able to hear God.
Ruth Haley Barton writes:
"There is nothing in Scripture to indicate that God has given up on speaking to us in dreams. In fact, in my work as a spiritual director I often encourage people to pay attention to their dreams because when we are asleep we are less ego-defended and more able to receive a prompting from God that is beyond what our cognitive faculties can accept." (Barton,Pursuing God's Will Together, 65)
If I have a dream that strikes me as being from God I write it down as soon as I can, with no embellishments and without interpretation. I take time to ask God about the meaning of the dream. At times I have submitted my dream to someone who is God-connected and has spiritual discernment (because no time to connect with God = no spiritual discernment).