Abdullah ibne-Qurt Radiyallahu anhu narrate
that Rasulullah Sallallahu alaihi wasallam
"On the Day of Judgement, the first thing that
a slave of Allah will be held accountable for is Salat.
If it is found sound and satisfactory, the rest of his deeds
will aslo be sound and satisfactory, and if found corrupt
and rotten, then the rest of his deeds will also be
corrupt and rotten"
(Source reported in Tabarani, Targhib)