(1) The thawab and spiritual benefits of saum are eliminated by commission of sin during the state of fasting.
(2) Fasting acts as a protecting shield for the Sa-im (fasting person) as long as he does not destroy his Saum with sin.
(3) Among the sins which destroy the benefits of Saum, the worst is Gheebat (to speak ill of others in their absence), Gheebat also produces physical weakness during Saum. The fast thus becomes very difficult to observe.
(4) Indulgence in futile acts, nonsensical and idle conversation are also negatory of the benefits of Saum.