‏الصيام : Hadeeth No:2380 Abu Huraira reported Allaah's Messenger (sallAllaahu alayhi wa sallam) as saying: Observe fast on sighting it (the new moon) and break it on sighting it. But if (due to clouds) the actual position of the month is concealed from you, you should then count thirty (days)....

‏الحج : Hadeeth No:3178 'A'isha (Allaah be pleased with her) reported: When we came to Medina, and it was an unhealthy, uncogenial place, Abu Bakr fell sick and Bilal also fell sick; and when Allaah's Messenger (sallAllaahu alayhi wa sallam) saw the illness of his Companions he said: O Allaah, make Medina as congenial to u...