Those who rehearse the Book of Allah, establish regular Prayer, and spend (in Charity) out of what We have provided for them, secretly and openly, hope for a Commerce that will never fail:
For He will pay them their meed, nay, He will give them (even) more out of His Bounty: For He is Oft-Forgiving, Most Ready to appreciate (service).[Qur'an 35:29-30]
'A'isha (RA) reported that the Messenger of Allah (PBUH) had ordered to observe fast (on 'ashura) before the fasting in Ramadan was made obligatory. But when it became obligatory, then he who wished fasted on the day of ashura, and he who wished did not observe it (on that day).