Is it permissible for a man to spit on his wife's vagina or anus without penetration, with or without her consent, and is it permissible to force her to do so?

This act is permissible with the wife's consent for the front or back, because the basic principle is permissibility unless there is evidence of prohibition. However, one should be cautious not to go too far in enjoying the back from the outside without penetration, for fear of falling into the forbidden. If it is without the wife's consent, then it is not permissible, because marital relations must be conducted in a reasonable manner that does not harm her.