The Prophet Muhammad (peace and blessings of Allah be upon him) told us how to protect ourselves from nightmares by reciting verses from the Quran and du’as narrated from him before going to sleep.

• Abu Sa’id al-Khudri narrated that he heard the Messenger of Allah (peace and blessings of Allah be upon him) say: “If any one of you sees a dream that he likes, it is from Allah, so let him praise Allah for it and tell people about it. But if he sees something other than that, that he dislikes, it is from the Shaitan, so let him seek refuge with Allah from its evil and not mention it to anyone, for it will not harm him.” (Narrated by al-Bukhari, 7045)

Shaykh Al-Islam Ibn Taymiyah and others said that it is possible for a person to see Allah in a dream. A person may see in his dream that Allah is speaking to him, but whatever images he sees is not Allah because there is nothing like unto Allah, so there is nothing that resembles Him.

It is possible for a person to see the Prophet (peace and blessings of Allah be upon him) in a dream, and the Shaitan cannot appear in the image of the Prophet (peace and blessings of Allah be upon him), but he could appear in another form and claim that he is the Prophet (peace and blessings of Allah be upon him).

Interpretation of dreams in Islam falls into various categories: 1- Dreams may be interpreted in light of the Quran, 2- or in light of the Sunnah, 3- or by means of the proverbs, 4- or by names and metaphors, 5- or in terms of opposites. For more, please see the detailed answer.