Sahih Muslim Book 1, Hadith Number 147.

Chapter : Application of the word “Kufr” on one who neglects prayer.

It is narrated on the authority of Abu Zubair that he heard Jabir b. ‘Abdullah saying. I heard the Messenger of Allah (may peace and blessings be upon him) observing this: Between man and polytheism and unbelief is the abandonment of salat.