Is it permissible to seek assistance from Prophet Muhammad (s) or his holy progeny (as)? Can this practice be supported by references from the Holy Quran?
Yes. It is permissible to seek help from the Prophet (SAWA) or his holy Progeny (AS) being the best servants of Allah whose prayers are accepted by Allah. We believe that nothing can happen with out the will of Allah, and His most humble servants can help us in seeking from Allah fulfilling our wishes. Quran tells us how Prophet Sulain did seek help from a pious servant of Allah to get the throne of Bilqees from Yemen to Palestine in a moment. Sura Naml, verse 40.
'Wassalam.