Prophet Muhammad's (ﷺ) last Sermon, mount Arafat
On the return of the sacred month of pilgrimage, the Prophet (ﷺ), under the presentiment of his approaching end, determined to make a farewell pilgrimage to Mecca. In February 632, he left Medina with a very considerable concourse of Muslims. It is stated that from ninety thousand to one hundred and forty thousand people accompanied the Prophet (ﷺ).

Before completing all rites of the pilgrimage, he (ﷺ) addressed the assembled multitude from the top of Mount Arafat in the following words:

• "O people! Listen to my words, for I know not whether another year will be vouchsafed to me after this year to find myself among you.
• Your lives and property are sacred and inviolable among one another until you appear before the Lord, as this day and this month are sacred for all; and remember, you will have to appear before your Lord Who will demand from you an account for all your actions.
• O people, you have rights over your wives, and your wives have a right over you.
• Verily you have taken them on the security of Allah and have made their people lawful unto you by the words of Allah.
• And your slaves, see that you feed them with such food as you eat yourselves, and clothe them with the stuff you wear, and if they commit a fault which you are not inclined to forgive, then part with them; for they are the servants of the Lord and are not to be harshly treated.
• O people, listen to my words and understand them. Know that all Muslims are brothers. You are one brotherhood; but no man shall take ought from his brother, unless by his free consent. Keep yourselves from injustice.
• Let him who is present tell this to him who is absent. It maybe that he who is told this afterward may remember better than he who has now heard it.

The Prophet(ﷺ) concluded his sermon by exclaiming: "O Lord, I have fulfilled my message and accomplished my work."

The assembled multitude, all in one voice, cried: "Yea, verily you have."

The Prophet(ﷺ) again exclaimed: "O Lord, I beseech You, bear witness to it."

Prophet returns to Madina
Having rigorously performed all the ceremonies of the pilgrimage, that his example might be followed by all Muslims for all succeeding ages, the Prophet(ﷺ) returned with his followers to Medina.

The eleventh year of the hijrah, being the last year of Muhammad's (ﷺ) life, was spent at Medina. There he settled the organization of the provincial and tribal communities which had adopted Islam and become the component parts of the Muslims federation. More officers had to be deputed to the interior provinces for the purpose of teaching their inhabitants the precepts of the religion, administering justice, and collecting Zakat.

Muadh Ibn Jabal (رضي الله عنه) was sent to Yemen. On his departure to that distant province the Prophet(ﷺ) enjoined him to use his own discretion in the event of his being unable to find express authority in the Quran. Ali(رضي الله عنه) was deputed to Yamama in the southeast of the peninsula.

To him the Prophet(ﷺ) said: "Never decide between any two parties who come to you for justice unless you first hear both of them."

Reference: From "Stories of the Prophets" by Al-Imam ibn Kathir