Masturbation is not prohibited not haram - No medical Harm Dr Zakir Naik

There is not textual evidence that masturbation is prohibited. Also there is no issue medically. According to Dr Zakir Naik, there are three groups of scholars on this issue.
Group 1 says it is haram
Group 2 says it is not haram but makrooh
Group 3 says it is mubah i.e. not a sin.