Musnad Ahmed: Hadith 2822

Your people are saying that the Messenger of Allah (ﷺ) went between as-Safa and al-Marwah on a camel, and that that is Sunnah. He said: They are telling the truth and they are lying. I said: How can they be telling the truth and lying? He said: He did go between as-Safa and al-Marwah on a camel, but that is not Sunnah. The people would not disperse from around the Messenger of Allah (ﷺ), and could not be pushed back, so he went [between as-Safa and al-Marwah] on a camel so that they could hear him and see where he was, but their hands could not touch him.