Musnad Ahmad 47:1

Yahya ibn Sa'id narrated to us, from Zakariyya, from al-Sha'bi, from al-Harith ibn Malik ibn al-Barsa', who said: I heard the Prophet, peace and blessings of Allah be upon him, on the day of the conquest of Makkah, saying: "This shall not be fought against—meaning—after today until the Day of Resurrection."