Allaah said:

فَخَلَفَ مِن بَعْدِهِمْ خَلْفٌ أَضَاعُوا الصَّلَاةَ وَاتَّبَعُوا الشَّهَوَاتِ  [trans: ”Then, there has succeeded them a posterity who have neglected the prayers and have followed lusts” فَسَوْفَ يَلْقَوْنَ غَيًّا [trans: ”So they will be punished with a severe manifold punishment”[For futher details, see: Tafseer Sadi]

Imaam Ibnul Qayyim (rahimahullaah) said:

The Sahaabah and the Taabi-een explained neglect of the prayer to mean offering them outside their fixed times. And certainly neglecting them includes the meaning of abandoning them, abandoning its proper times, its obligations and pillars. Also the one who deliberately delays them beyond their fixed times is a transgressor of the limits imposed by Allaah and likewise is the one who prays them before their fixed times. [Badaa-I At-Tafseer Al-Jaami Limaa Fassarahu Al-Imaam Ibnu Qayyim Al-Jawziyyah: page: 175: Vol: 2] 

Very Important

Conditions, Pillars and obligations of the prayer

See Link

http://www.salafitalk.net/st/viewmessages.cfm?Forum=10&Topic=8984