Fasting the month of Ramadan was enjoined in 2 AH, and the Messenger of Allah (peace and blessings of Allah be upon him) fasted nine Ramadans.
Al-Nawawi (may Allah have mercy on him) said in al-Majmu’ (6/250)”
“The Messenger of Allah (peace and blessings of Allaah be upon him) fasted Ramadan for nine years, because it was enjoined in Sha’ban 2 AH, and the Prophet (peace and blessings of Allaah be upon him) died in Rabi’ al-Awwal 11 AH.”
And Allah knows best.
