Answer
Asalamu Alaikum Brother,
Thank you for contacting About Islam with your question.
I think that, first, we must know the meaning of the word vision (ru’yah in Arabic) and the difference between a vision and a dream (hulm in Arabic).
The Vision in Islam
A vision can be defined as a vivid mental image whether it was in sleep or in wakefulness.
The Quran tells us that the vision has roots in the religion of Islam. Allah Almighty told us about the vision of Prophet Abraham. The Quran says:
{Then, when [the son] reached [the age of serious] work with him, he said: “O my son! I see in a vision that I offer you in sacrifice: Now see what is your view!” [The son] said: “O my father! Do as you are commanded: you will find me, if Allah so wills, one practicing patience and constancy!”} (As-Saffat 37:102).
Also Prophet Muhammad saw lots of visions:
While I was sleeping, the treasures of the earth were presented to me and I was made to wear on my hands two gold bangles. I felt a sort of burden upon me and I was disturbed and it was suggested to me that I should blow over them. So, I blew and both of them disappeared. I interpreted them as two great liars who would appear at any time, one is the inhabitant of Sana’ and the other is that of Yamama. (Sahih Muslim)
So, the Quran and Sunnah mention to us examples of visions, as they were a part of prophecy. But we cannot say that every dream is a vision, for our beloved Prophet (PBUH) explained to us the difference between a dream and a vision:
I used to see dreams and was so much perturbed that I began to quiver and have a temperature, but did not cover myself with a mantle. I met Abu Qatada and made a mention of that to him. He said: I heard Allah’s Messenger (may peace be upon him) as saying: A good vision comes from Allah and a [bad] dream (hulm) from the devil. So, when one of you sees a bad dream (hulm) which he does not like, he should spit on his left side thrice and seek refuge with Allah from its evil; then it will not harm him. (Sahih Muslim)
The Dream in Islam
As for your question about dreaming of our beloved Prophet Muhammad (PBUH), the Messenger of God said:
He who saw me in a dream in fact saw me, for Satan does not appear in my form. (Sahih Muslim)
The Prophet also said:
Whoever has seen me in a dream, then no doubt he has seen me for Satan cannot imitate my shape. (Sahih Al-Bukhari)
I ask Allah Almighty to gather us with our Prophet Muhammad (PBUH) in Paradise. Ameen.
Thank you again for your question and please keep in touch.
Walaikum Asalam.
Please continue feeding your curiosity, and find more info in the following links:
Interpretation of Dreams: Islamic View