Ibn Ishāq said (1):
According to what has reached me from Abū Salamah ibn ‘Abd al-Rahmān—and we seek refuge in Allah from attributing to the Messenger of Allah, may Allah bless him and grant him peace, anything he did not say—the Messenger of Allah’s first sermon was delivered as follows: he stood among them, praised Allah and extolled Him as He deserves, then said:
“To proceed, O people, send good deeds ahead for yourselves. Know for certain: by Allah, each of you will surely die and leave his sheep without a shepherd. Then his Lord will surely say to him—with neither an interpreter nor a chamberlain barring him from his Lord—‘Did My messenger not come to you and convey the message to you? Did I not give you wealth and bestow My bounty upon you? What, then, have you sent ahead for yourself?’ He will surely look to his right and left and see nothing. Then he will surely look ahead and see nothing but Hell. Whoever can shield (2) his face from the Fire, even with half a date, should do so. Whoever has nothing to give should do so with a kind word, for a good deed done in this way is rewarded ten (3) times over, up to seven hundred times. Peace be upon you, and the mercy of Allah (4) and His blessings.”
(1) Al-Sīrah (The Prophet’s Biography) by Ibn Hishām (1/500). Also transmitted by Hannād ibn al-Sarī in al-Zuhd (Asceticism) (492) and al-Bayhaqī in Dalā’il al-Nubuwwah (The Signs of Prophethood) (2/524), through Yūnus ibn Bukayr, from Muhammad ibn Ishāq, who said: “Al-Mughīrah ibn ‘Uthmān ibn Muhammad ibn ‘Uthmān ibn al-Akhnas ibn Sharīq narrated to me, from Abū Salamah ibn ‘Abd al-Rahmān ibn ‘Awf, who said: ‘The Prophet’s first sermon in Medina, may Allah bless him and grant him peace, was as follows: he stood among them …’” The hadith is therefore mursal (reported directly from the Prophet by a Successor, without naming an intermediary).
Note: The manuscript of Hannād’s al-Zuhd contained wording substantially as quoted above. However, its editor conjecturally altered the chain of transmission to read: “Al-Mughīrah ibn ‘Uthmān narrated to me, from Muhammad ibn ‘Uthmān ibn al-Akhnas ibn Sharīq.” The reading in the manuscript of al-Zuhd and in al-Bayhaqī’s account is further supported by Ibn Kathīr’s quotation in al-Bidāyah wa-l-Nihāyah (The Beginning and the End) (4/528), and likewise by Ibn Rajab’s quotation in Fath al-Bārī (5/387).
(2) Qāf and Mīm read “yattaqī (protects).”
(3) Kāf and ‘Ayn read “bi-‘ashr (by ten).”
(4) The name Allah is absent from Mīm.