Abu Dawud

680. Commentary: Certainly, whoever is firm in creed and sincerely acknowledges these matters, Allah, exalted is He, truly forgives him, no matter how many sins he may have committed. After all, who can stand between His forgiveness and the servant?

Hadith Commentary: Benefits and Issues:
Whoever receives the call to your Prophethood and Messengership, and does not believe in you nor adopts the religion you have brought as his own religion, and dies in that state, will enter Hellfire, even if he is a follower of a previous Messenger’s religion and his book, whether he be a Jew or a Christian.

In short, after your (sallallahu alayhi wa sallam) advent, salvation is not possible without believing in you and accepting your Shari‘ah.

The concept of “unity of religions”—that one may adopt any revealed religion, become a monotheist, and that this alone suffices for salvation—is a misguided and atheistic notion.

Commentary:
(1)
The acknowledgment of monotheism (tawhid) and messengership (risalah) is the foundation of Islam, and salvation depends upon it.

(2)
Being content with Allah’s Lordship (rububiyyah) means to have such faith in His Lordship as is the due right of faith.
The awareness that all blessings are being given to us by Him alone, and that He is continuously providing everything we need, generates a feeling of gratitude and love. For this reason, a believer’s love for Allah is unparalleled.
This love motivates him to perform every good deed in order to attain further closeness to Him, and compels him to avoid every sin.
After this, all hopes become attached to Allah alone. Whoever attains this station will certainly enter Paradise by Allah’s mercy.

(3)
Accepting Islam as one’s religion means to develop the conviction that every aspect of this religion is true, and every guidance is precisely correct, in which there is no defect or flaw of any kind.
No belief, custom, or etiquette of non-Muslims is superior to the great civilization of Islam.
When this awareness is developed, it is no longer possible for us to look towards non-Muslims for guidance in any matter; rather, in every field of life and every aspect of living, guidance is found in the teachings of Islam, and the heart is content with it.
In reality, this is the faith that is missing in most Muslims today; this is the reason why every Muslim society has, in practice, become a non-Muslim society and is deprived of the blessings of Islam.

(4)
Being content with the prophethood and messengership of Muhammad (sallallahu alayhi wa sallam) means that his noble example (uswah hasanah) is the true interpretation of Islam, and acting upon it is our objective.
The laws (shari‘ahs) of the previous prophets (alayhim as-salam) have been abrogated.
We have no need to act upon them.
Similarly, no follower (ummah member) holds such a status that every statement of his should be accepted blindly.
The center and axis of the unity of Muslims is only the blessed person of the Messenger of Allah (sallallahu alayhi wa sallam).
As Allamah Iqbal (rahimahullah) has said:
“Bih Mustafa bar-san khwesh ra keh deen hama oost
Agar bih oo na raseedi tamam Bolehabist”
Bring yourself to Mustafa (sallallahu alayhi wa sallam), for his very being is the entirety of the religion.
If you do not reach him, then everything else is merely the way of Abu Lahab.