How can we reconcile the Prophet's fasting of Ashura in Medina for ten years with his saying, "If I live until next year, I shall certainly fast the ninth"?

The questioner's mention that the Prophet, peace and blessings be upon him, said: "If I live until next year, I shall certainly fast on the ninth," does not align with the authentic narrations on this matter. The correct account is that he, peace and blessings be upon him, only said this less than a year before his death. What happened when he arrived in Medina was that he saw the Jews fasting on Ashura, so he asked: "What is this?" They replied: "This is a day when Allah saved the Children of Israel from their enemy, so Musa fasted it." The Prophet, peace and blessings be upon him, then said: "I am more deserving of Musa than you," so he fasted it and commanded its fasting.

Quraysh used to fast on Ashura during the pre-Islamic era (Jahiliyyah), and the Messenger of Allah, peace and blessings be upon him, used to fast it before the Hijra. His fasting of it was not in imitation of the Jews.

Ultimately, and before his death, the Prophet, peace and blessings be upon him, wished to differ from the People of the Book, so he said: "If I live until next year, I shall certainly fast on the ninth," so that fasting the ninth and the tenth would be a divergence from them. Fasting the Day of Ashura is a recommended Sunnah, and the Prophet, peace and blessings be upon him, did not fast it in imitation of the Jews.