Musnad Ahmad 830:14

Isma'il narrated to us, Ayyub informed us, from Muhammad ibn Sirin, from Abu Bakrah, that the Prophet, peace and blessings of Allah be upon him, delivered a sermon during his pilgrimage and said: "Behold, time has turned as it was on the day Allah created the heavens and the earth. The year is twelve months, of which four are sacred: three consecutive—Dhu al-Qa'dah, Dhu al-Hijjah, and Muharram—and Rajab of Mudar, which is between Jumada and Sha'ban." Then he said: "Which day is this?" We said: "Allah and His Messenger know best." He remained silent until we thought he would name it by a name other than its own. He said: "Is it not the Day of Sacrifice (Yawm al-Nahr)?" We said: "Yes." Then he said: "Which month is this?" We said: "Allah and His Messenger know best." He remained silent until we thought he would name it by a name other than its own. He said: "Is it not Dhu al-Hijjah?" We said: "Yes." Then he said: "Which land is this?" We said: "Allah and His Messenger know best." He remained silent until we thought he would name it by a name other than its own. He said: "Is it not the Sacred City (al-Baldah)?" We said: "Yes." He said: "Indeed, your blood and your wealth—and I think he said: and your honor—are sacred to you, like the sanctity of this day of yours, in this month of yours, in this land of yours. You will meet your Lord, and He will ask you about your deeds. Beware, do not return after me as disbelievers, striking the necks of one another. Have I conveyed the message? Let the witness among you convey it to the absent, for perhaps the one to whom it is conveyed will be more mindful of it than some of those who hear it." Muhammad said: "And that was indeed the case." He said: "Some of those to whom it was conveyed were more mindful of it than some of those who heard it."