Abdullah bin Buraydah narrates from his father, Sayyiduna Buraydah bin al-Husayb (may Allah be pleased with him), that the Messenger of Allah (peace and blessings be upon him) said: "The covenant between us and them (the disbelievers) is the prayer; so whoever abandons it (the prayer) has committed disbelief."
In the narration of Ali (bin al-Hasan bin Shaqiq), he said: "The Messenger of Allah (peace and blessings be upon him) said", and the rest is the same.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب صلاة الاستسقاء / 6499