In the name of Allah, The Most
Gracious, the Most Merciful.

Ever since people innovated the dogma of Shirk (i.e.
joining others in worship along with Allah), Allah had been sending Prophets
and Messengers to his devotees in order to invite them to the worship of Allah
and Allah Alone, to order them not to ascribe partners to Him and bring them
out of the darkness of polytheism into the light of Monotheism. All the
Prophets preached Tawhid (i.e. Monotheism, the Belief in the Oneness of Allah,
the Glorious, and the Elevated). The following verses from the Noble Quran
illustrate this fact:

“Indeed We sent Nûh (Noah) to his people, and he said:
O my people! Worship Allah! You have no other Ilâh (God) but Him. (Lâ ilaha
illallah, none has the right to be worshipped but Allah). Certainly, I fear for
you the torment of a Great Day!” (V. 7:59).

“And to ‘Âd (people, We sent) their brother Hûd. He said:
‘O my people! Worship Allah! You have no other llâh (God) but Him. (Lâ ilaha
illallah, none has the right to be worshipped but Allah). Will you not fear (Allah)?”
(V.7:65).

“And to the people of) Madyan, (We sent) their brother
Shu`aib. He said: O my people! Worship Allah you have no other llâh (God) but
Him. (Lâ ilaha illallah, none has the right to be worshipped but Allah).
Verily, a clear proof (sign) from your Lord has come to you, so give full
measure and full weight and wrong not men in their things, and do not make
mischief on the earth after it has been set in order that will be better for
you if you are believers.” (V.7:85)

“And to Thamûd (people, We sent) their brother
Salîh. He said: ‘O my people! Worship Allah! You have no other Ilâh (God) but
Him. (Lâ ilaha illallah, none has the right to be worshipped but Allah).”
(V.7:73)

“And verily, We have sent among every Ummah
(community, nation) a Messenger (proclaiming): Worship Allah (Alone) and avoid
(or keep away from) Tâghût ” (all false deities, i.e. do not worship Tâghût
besides Allah).” (V. 16:36)

Every Prophet
was sent to his own nation for their guidance, but the message of Prophet
Muhammad as we will do was general for all mankind and jinn. As in Surat al
A’raf (Allâh addresses His Messenger PBUH):

“Say (O
Muhammad PBUH): ‘O mankind! Verily, I am sent to you all as the messenger of
Allâh.'” (V.7:158).

So the aim of
sending these Prophets and Messengers to mankind and jinn was only that they
should worship Allâh Alone as Allâh Almighty said:

“And I (Allâh)
created not the jinn and mankind except that they should worship Me (Alone)”
(V.51:56).

And to
worship, Allâh means to obey Him and to do all that He has ordained, and to
fear Him by abstaining from all He has forbidden.

Then those who obey Allâh will be rewarded in
Paradise, but those who will disobey Him will be punished in Hell-fire.