Can a dream be a sin?

I am a young male and I am struggling to overcome temptation and impurity. I go to confession often and try to go to mass everyday. I was wondering, if I have an impure dream, does that mean that I have sinned? If so, is this a mortal sin?

Dear big,

It is impossible to sin in one’s sleep. In order to sin, one must have the use of his free will. No matter how much one may feel that he has his free will in his dreams, he doesn’t.

Fr. Vincent Serpa, O.P.

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