Sayyiduna Jabir bin Abdullah (may Allah be pleased with them both) narrates that the Messenger of Allah (peace and blessings be upon him) said: "The difference between the believing servant and the disbeliever is abandoning the prayer."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الاستسقاء / 6498