Fifth Matter: Can a person who says “La ilaha illallah (There is no god but Allah)” but does not say “Muhammadun Rasulullah (Muhammad is the Messenger of Allah)” find salvation?
S e c o n d l y : You ask in your letter whether There is no god but Allah is sufficient on its own. That is, intending the second part, you ask: can someone who does not say Muhammad is the Messenger of Allah find salvation? The answer to this is lengthy, so for now we shall only say this:
The two parts of the confession of faith cannot be separated; they prove each other, comprise each other; one cannot be without the other. Since the Prophet (Upon whom be blessings and peace) was the Seal of the Prophets and the heir of all the prophets, he is at the start of all the ways leading to Allah. There can be no way to reality and salvation outside his mighty highway. All those with inner knowledge of Allah and the authorities of those who have researched into reality have said like Sa‘di Shirazi: “It is impossible, Sa‘di, to be victorious on the way of salvation, except by following Mustafa.” They also said: “All ways are closed except the highway of Muhammad.”
However, it sometimes happens that people may be on the highway of Muhammad (PBUH) and within it, without knowing that it is the highway of Muhammad.
And it sometimes happens that they do not know the Prophet, but the road they take is part of the highway of Muhammad (PBUH).
It happens too that being in a state of ecstasy or entirely immersed in contemplation or having withdrawn from the world, not thinking of the highway of Muhammad, There is no god but Allah is sufficient for them. Nevertheless, a most important aspect is this: non-acceptance is one thing, while the acceptance of non-being is another. Ecstatics and recluses or those who have not heard or do not know, do not know the Prophet or they do not think of him so that they should accept him. They are ignorant in that respect. They only know There is no god but Allah in regard to knowledge of Allah. They may be among those who will be saved. But if those who have heard of the Prophet and know his message do not affirm him, they do not recognize Almighty Allah. For them, the phrase There is no god but Allah alone does not express the affirmation of Divine Unity, which is the means of salvation. For that is not ignorant non-acceptance, which may be excusable to a degree, it is rather the acceptance of non-being, which is denial. A person who denies Muhammad (Upon whom be blessings and peace), who with his miracles and works was the pride of the universe and glory of mankind, certainly can in no respect receive any light and will not recognize Allah. However... that is enough for now.