Praise be to Allaah.
Your friend has to realize that that this habit is haraam
according to sharee’ah, as is indicated in the Book of Allaah and the Sunnah
of His Prophet (peace and blessings of Allaah be upon him). We have
already quoted the evidence in detail in question no
329. This habit is
something that is repulsive to sound human nature and reason, and it is not
befitting for a Muslim to lower himself to this level.
It should also be noted that sin has negative consequences a
person, in this world and in the Hereafter, if he does not repent and if
Allaah does not bestow His mercy upon him. We have already discussed this in
the following questions:
This habit has many harmful effects, such as
weakening the body, and increasing the gulf between a person and his Lord.
It is one of the major factors in depression.
With regard to the matter mentioned in the question, if he
ejaculated as a result of masturbation then his fast is invalidated and he
has sinned; he has to refrain from eating and drinking for the rest of the
day, and he also has to make up that day.
We have already discussed this in detail in the answer to questions no. 38074
and 2571. And Allaah knows best.