‏الصيام : Hadeeth No:2410 Samura b. Jundub addressed and narrated from the Prophet of Allaah (sallAllaahu alayhi wa sallam) having said (these words): Neither the call of Bilal should mislead you nor this whiteness (of false dawn) till (the true) dawn appears (or he said) till the dawn breaks....

‏البر والصلة والآداب‏ : Hadeeth No:6283 Umm Darda' reported on the authority of Abu Darda' as saying: I heard Allaah's Messenger (sallAllaahu alayhi wa sallam) as saying: The invoker of curse would neither be witness nor intercessor on the Day of Resurrection....