‏الصلاة : Hadeeth No:1726 Ibn Mas'ud reported Allaah's Messenger (sallAllaahu alayhi wa sallam) as saying: Wretched is the man who says: I forgot such and such a sura, or I forget such and such a verse, but he has been made to forget....

‏الصيام : Hadeeth No:2379 Abu Huraira reported Allaah's Messenger (sallAllaahu alayhi wa sallam) as saying: Observe fast on sighting it (the new moon) and break (fast) on sighting it (the new moon), but if the sky is cloudy for you, then complete the number (of thirty)....