بِسْمِ اللهِ الرَّحْمَـنِ الرَّحِيمِ

All praise is for Allah; peace and prayers be upon Muhammad his family, his Companions and all those who follow in their footsteps until the Day of Judgement.

Allah's command came to the Prophet to engage in Da’wah: "O you
enveloped (in garments)! Arise and warn!”
[Surah Al-Muddathir (74), Ayat 1-2.]

The Prophet obeyed the command and began to call people to his Lord,
secretly for three years until Allah (SWT) revealed the verse (which means) :
"Therefore proclaim openly that which you are commanded, and turn
away from those who join false gods with Allah."
[Surah Al-Hijr (15), Ayah 94.]

It was then that the Prophet Muhammad ascended Mount As-Safaa and
collected upon the clans of Qur'aish: "I have come to you with a warning against a
severe punishment." 53 For the following twenty-three years, Da’wah became the
preoccupation of the Prophet and the pivot of his life until his death.
The Messenger of Allah called the people of Makkah, freemen and slaves,
young and old, to the worship of Allah. He extended the Da’wah to visitors who came
to Makkah on pilgrimage or for trade. He went to Taa'if to deliver Da'wah to the tribe
of Thaqeef. Following the pledge of allegiance at al-'Aqabah, he sent Musa'b bin
`Umair to Madeenah in order to call its people to the worship of Allah. Later, he
himself emigrated to Madeenah and set up his mosque where he preached to the
newly formed community "as a witness, a bearer of glad tidings, a warner, and
as one who invites to Allah by His leave.". He frequented the assemblies of the
Ansaar tribe, preaching and teaching. He sent his preachers throughout the Arabian
Peninsula: Mu'adh bin Jabal went to Yemen to call upon the 'People of the Book'
there to Islam; 'Urwah bin Mas'ood went to Thaqeef to call his own people to the new
religion; `Alaa' bin al-Hadhramee was sent to Bahrain. Even the Prophet himself
stood by the gate of Ka'bah after the Conquest of f Makkah, calling the Makkans to
Islam. On his return to Madeenah, tribal delegations flocked to him from all over
Arabia (in a year that came to be known as the ‘Year of Delegations'), whereupon
they responded to his call by embracing the new religion and returning to their
homes to call upon their tribes and kin to follow in their footsteps.

With the entire land of Arabia now entered into the Islamic faith, the Prophet
now sent his emissaries with the message of Islam to the kings and emperors
around the Arabian Peninsula:
"In the Name of Allah, the Most Gracious, the Most Merciful. From Muhammad,
the Messenger of Allah, to Heraclius, the Emperor of the Romans. Peace be upon him
who follows the true guidance. To proceed, I extend to you the invitation to accept
Islam. Embrace Islam and you will be safe. Accept Islam and Allah will give you a
double reward. And if you turn away, upon you will be the sins of your subjects:
“Say: ‘O People of the Book, come to the word that is just between us
and you, that we worship none but Allah, and we associate no partners with Him, and that none of us take others as lords besides Allah.' Then, if they
turn away, say: ’Bear witness that we are Muslims.’ ”

53 Bukhari and Muslim.
54 Surah Al-Ahzaab (33), Ayat 45-46.
And in the farewell pilgrimage (Hajjatul-Wadaa'), thousands upon thousands of
Muslims stood listening to the call of the Prophet :
"Verily, everything related to Jahiliyyah is now under my feet..." and "I have
left you with something which, if you hold on to, You will never go astray: the Book
of Allah and the Sunnah of His Messenger.”
During his last illness which led to his demise, the Prophet entered the
mosque with his head bandaged, and sat on his mimbar and said, "...By Allah, I have
no fear that you might revert to polytheism after my death. What I fear for you is
the life of this world and your rivalry therein."