It is narrated from Sayyiduna Ibn Amr (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said to me: "Recite the Qur'an once a month." I said, "I have strength for more than that." I kept requesting continuously until the Noble Prophet (peace and blessings be upon him) said: "Recite the Qur'an in five days, and fast three days in a month." I said, "I have strength for more than that." The Noble Prophet (peace and blessings be upon him) said: "Then fast in the manner that is most beloved to Allah, and it is the way of Sayyiduna Dawood (peace be upon him): he would fast one day and leave fasting the next day."
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 6843