Dreaming of slapping someone may indicate that you want to teach that person something or change their attitude. It can sometimes serve as a reminder of your generosity or willingness to help, which you feel is not being properly appreciated by the other party. Such dreams may reflect pressure or discomfort within you, where you wish to express your emotions towards others.
From Imam Muhammad Ibn Seerin's Dictionary of Dreams According to Islamic Inner Traditions â entry "Smack" (page 397) â resolved via the equivalent "Slapping on the cheek" entry.
To lightly slap someone in a dream means to reprimand him, or to oblige him to recognize a favor, boasting about one's generosity, or constantly reminding the other person of some shabby assistance. Ifone playfully slaps someone lightly on his cheek in a dream, it also means that the latter owes him something or a favor and the opposite is interpreted accordingly. Slapping someone's face with anger in a dream means that the victim will triumph over the assailant. To slap someone in a dream also means recognition of his seniority or superiority. Threatening someone in a dream also maybe a recognition of his superiority. (Also see Digging up the past; Slapping; Threat)
Note: Islamic dream interpretation depends on the dreamer's circumstances and state. This is a general guide drawn directly from the source book.
