Prophet Muhammad as the Spirit of all Guides.

[Abu Hafsat]

As-Salaam alaikum,

 Being the nearest to the Absolute, Prophet Muhammad, Sallallahu alaihi Wasallam, is the nearest created being to absolute perfection. This is why the outpouring of Divine Mercy from Allah Ta'ala toward creation is concentrated on him and radiates from him to pervade all the degrees of existence. And this is what is meant by the expression Sallallahu alaihi, translated as 'may Allah's blessings be upon him'.   As for Wa-Sallam, which means 'and peace be upon him'  it is the ability to receive this influx of Divine Lights and yet remain firm and serene.