Musnad Ahmad 28:386

'Affan narrated to us, Sulaym ibn Hayyan narrated to us, Sa'id ibn Mina narrated to us, I heard 'Abdullah ibn 'Amr saying: The Messenger of Allah (ﷺ) said to me: "O 'Abdullah ibn 'Amr, it has reached me that you fast the day and stand in prayer the night. Do not do that, for your body has a right over you, and your wife has a right over you, and your eyes have a right over you. Break your fast and fast three days of every month, for that is the fasting of a lifetime." I said: "O Messenger of Allah, I find that I have strength." He said: "Fast the fasting of Dawud; fast one day and break your fast one day." 'Abdullah used to say: "I wish I had taken the concession."