Masturbation prohibits procreation. The husband was to be head of the home and care for the wife. Therefore as the church is subject unto Christ, so let the wives be to their own husbands in every thing. Masturbation is self-centered. Nevertheless, to avoid fornication, let every man have his own wife, and let every woman have her own husband.
Masturbation brings self gratification.
Wherefore they are no more twain, but one flesh. Masturbation does not promote the one flesh relationship between a husband and wife. Sexual desires for the opposite sex are natural. Often masturbation and homosexuality or sodomy are linked. Masturbation seems to fit here.