An Extract from Al-Mawaahibul-Ladunya by Al Imam Al Qastalani (Radi Allahu Anhu)

The Pecedence in the Prophethood of Sayyiduna RasulAllah (Sallal Laahu Alayhi Wasallam)

Hadrat Abdullah bin Amr bin Ausi (Radi Allahu Anhu) narrates that the Holy Prophet (Sallal Laahu Alayhi Wasallam) has said, "Indeed, 50 000 years before the creation of the heavens and earth, Allah (The Exalted) recorded the Taqdeer (fate) of the creation. (At that time) His Arsh (heaven) was on water" 

"Muhammad is the Khatamun Nabiyeen (Seal of the Prophets)" was amongst that written on the Lauh-e-Mahfooz (Protected Tablet).

Hadrat Arbaaz bin Sariya (Radi Allahu Anhu) reports that the Noble Messenger (Sallal Laahu Alayhi Wasallam)  has stated, "I was already the final Nabi in the sight of Allah (The Exalted), even when Adam was being created" 

Imaam Haakim (Radi Allahu Anhu) has classified the sanad (chain of narrators) of this Hadith as sahih.

THE ARTICLE IN PDF FORMAT CAN BE VIEWED HERE:THE DISTINCTIVE PREEMINENCE OF THE FINAL MESSENGER
Imam Al Qastalani (Radi Allahu Anhu)