"Lord of the heavens and of the earth, and of all that is between them: so worship Him, and be constant and patient in His worship: knowest thou of any who is worthy of the same Name as He?"[Qur'an 19:65]

Narrated Alqama(RA): I asked 'Aisha(RA) "Did Allah s Apostle(PBUH), use to choose some special days (for fasting)?" She replied, "No, but he used to be regular (constant) (in his service of worshipping). Who amongst you can endure what Allah's Apostle used to endure?"