A:Imam Fakhruddeen Raazi has explained the differences between a Rasool (prophet) and a Nabi (messenger). A Rasool is one who has performed miracles and has received a new Divine book. He establishes a new code of law (Shar’iah) and abrogates the previous code of law and book. He has also visibly seen the angel that comes with the Divine message, and the Rasool is commanded to invite the people towards the Deen.
A Nabi is one who is not given a new book, but rather establishes the book which was revealed to the Rasool before him. He does not abrogate the book and the code of law which was in vogue before him. He sees the angel in a dream or the Rasool of the time informs him that he has been chosen as a Nabi. (Tafseer Raazi V1 p3212, Mafaateehul Ghayb V23 p43)
The Taurah served as a code of law for his people. The Zaboor revealed to him did not consist of a new code of law. The Zaboor contained mostly praises of Allah Ta’aala, advices and words of wisdom. It also foretold the advent of Rasulullah (Sallallaahu Alayhi wa Sallam). The Zaboor was revealed on the 12th night of Ramadhaan to Nabi Dawood (Alayhis Salaam). He was a Nabi.
Allah Ta’aala knows best.
Moulana Yusuf Laher