(Muhammadan Rasul Allah) is the second half of the Islamic Testimony of Faith (shahadah). Muhammad is the one sent by Allah. He is the representative of Allah. Without him we cannot come to know Allah. His message is the message of beautiful return to Allah. But, Muhammad is from the Light of Allah. So, before Muhammad can be the Messenger of Allah, Allah must be the Messenger of Muhammad. His Light sends out the message of Muhammad. Allah is the Messenger of Muhammad (Allah Rasul Muhammad) and then Muhammad is the Messenger of Allah (Muhammadan Rasulullah).
(La ilaha il Allah). These words which form the first part of the Islamic Testimony of Faith could be paraphrased as 'there is no reality, only Reality' or 'there is no truth, only Truth' or 'there is no love, only Love'. The phrase is the supreme declaration of Unity. "There is no god" (La ilaha) is the negation of everything that is other-than-Allah while "only Allah" (il Allah) is the affirmation that there is only Allah. Through the dhikr of "La ilaha il Allah" the one who remembers uses the word of negation - 'la' - to sweep away all of the inner debris which is defiling his heart, the Sacred Centre. Ultimately, by the Grace of Allah, the phrase "La ilaha il Allah" is replaced by the Word of the Essence Itself - Allah. Everything other-than-Allah has been negated. Allah is affirmed.
There is no divinity save the sole Divinity. The Principle insofar as It excludes and annuls the illusory World, while at the same time affirming the unique and supreme Reality. The mystery of Negation and of Affirmation of Reality (Nafy wal Ithbat).