The importance of prayer from the Koranic viewpoint
The following koranic verses indicate the importance of prayer:
1. You who believe, remember God often. Celebrate him morning and evening he is the one who accepts prayers from you, as do his angels, to lead you out of darkness into Light. He is Merciful with believer. (33:41-43)
2. Keep up prayer, pay the welfare tax, and obey the Messenger so that you may receive mercy. (24:56)
3.I [God] shall be with you if you keep up prayer and pay the welfare tax, and believe in My messengers and respect them , and advance God a handsome loan.(5:12)
4. This is a blessed Book we have sent down to confirm whatever came before it, so you may warn the Mother of towns and anyone around her, those who believe in it and attend to their prayer. (6:92)
5. Once you have finished praying, remember God while standing, sitting and [lying] on your sides. Even when you are at leisure, still keep up prayer: is a timely prescription for believers. (4:103)
Sources :
Nemuneh Koranic Exegesis (Naser Makarem)
The Noble Koran (English translation by T.B.Irving)