Volume 3, Book 31, Number 199:
Narrated Mujahid from ‘Abdullah bin ‘Amr:
The Prophet said (to ‘Abdullah), “Fast three days a month.” ‘Abdullah said, (to the Prophet) “I am
able to fast more than that.” They kept on arguing on this matter till the Prophet said, “Fast on altern –
ate days, and recite the whole Qur’an once a month.” ‘Abdullah said, “I can recite more (in a month),”
and the argument went on till the Prophet said, “Recite the Qur’an once each three days.” (i.e. you
must not recite the whole Qur’an in less than three days).