Obedience To Allah
Allah Most High says in the holy Quran: -
“He who obeys the Messenger has indeed obeyed Allah, but he who turns away, then we have sent you as a watcher over them.” (IV: 80)
The divine statement is very clear that whoever obeys the messenger
in fact obeys Allah in the true sense and he who disobeys him disobeys
Allah, because the Holy Prophet 
does not say anything on his own; on the contrary, all his statements and
acts used to be in accordance with the divine revelation. This fact, as
such, has been mentioned in several places in the Quran. The divine statement
in Surah-An-Najm is: -
“Nor does he speak of (his own) desire. It is only a revelation revealed. He has been taught (this Quran) by one mighty in power (Jibril).” (LIII: 3-5)
Commenting upon this verse Allamah Ibn Kathir writes that the Holy Prophet's
knowledge is perfect and his action is in accordance with his knowledge.
His path is straight. He is the legislator of the law (Shari'ah) and he
maintains the path of moderation. No statement or order of his is the outcome
of his own desire and selfish motives. He used to speak out only against
those things for which he was ordered by Allah, and that alone used to
be expressed by his auspicious tongue. His holy speech is free from suppression
and addition, loss or excess. It is stated in Musnad-e Ahmed that (once)
the Holy Prophet
said: "Through the intercession of a single man who will not be a prophet,
people equal to those of two tribes or of one tribe will enter Paradise.
Those two tribes are the tribe of Rabe'a and the tribe of Muzir." At this
a man said: "Isn't the tribe of Rabe'a among the tribe of Muzir" (that
you counted them separately). He said: I say only that which I am made
to speak."
There is another hadith in the Musnad-e-Ahmed to the effect that Hazrat
Abdullah bin Amr bin al-Aas 
reported: "Whatever I used to hear from the Holy Prophet
I used to write down for committing to memory. But some Quraishites prevented
me from doing so and said: 'The Holy Prophet
too is a human being; sometimes he speaks out in anger and displeasure
also." So I stopped writing. Then I mentioned this thing to the Holy Prophet
He said: "Keep jotting it down. By Allah in Whose possession is my life!
Nothing but the truth comes out of my tongue."
It says in a Hadith in the Musnad-e Bazzar that the Holy Prophet
said: "Whichever thing I report to you from Allah Most High is always free
from doubt and suspicion." It says in another Hadith that he
said: "I never speak nothing but the truth." At this some Companions said:
"But your holiness sometimes also indulges in pleasantry?” He replied:
"In pleasantries too the untrue does not come out of my tongue."
It is for this reason that Allah Most High hath ordered the people to
follow him because obedience to him is in fact obedience to Allah, as the
Holy Prophet
has said: - "He who obeyed me obeyed Allah undoubtedly and he who disobeyed
me disobeyed Allah undoubtedly. And he who obeyed my amir (commander appointed
by me), obeyed me and he who disobeyed my amir disobeyed me."
Why should not the transgression against the Apostle be transgression against Allah when Allah Most Glorious Himself states:
"Nor doth he speak of (his own) desire: It is naught save an inspiration that is inspired."
Hence not to believe in his statement is to reject Allah's statement.
