The poorly-cited Wikipedia article states:
The Farewell Sermon (Arabic: خطبة الوداع, Khuṭbatu l-Wadā), also known as Muhammad's Final Sermon or The Last Sermon, was delivered by Muhammad on the 9th of Dhu al-Hijjah, 10 AH (9 March 632) in the Uranah valley of Mount Arafat.
Whether Mohammed existed doesn't concern me, but this page states that his famed "Last Sermon" is a fake from 1991.
The top of 4.630.000 Google results for "last sermon" are indeed unsourced.
As my last Facebook comment quoting it got censored without comment, I'd like to know whether that part ("You will neither inflict nor suffer any inequity.") was representative of the religion of Islam.