Sayyiduna Ka'b bin Ujrah (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) came out to us while we were seven men, four of our mawali (freed slaves and clients) and three of our Arabs, sitting with our backs leaning against his mosque. He (peace and blessings be upon him) said: "What has made you sit here?" We said: "We are waiting for the prayer." He said: He remained silent for a little while, then turned his face towards us and said: "Do you know what your Lord says?" We said: "No." He (peace and blessings be upon him) said: "Your Lord says: Whoever prays the prayer at its time, guards it and does not waste it by belittling its right, then he has a covenant with Me that I will admit him to Paradise. And whoever does not pray it at its time and does not guard it, belittling its right, then he has no covenant with Me; if I wish I will punish him, and if I wish I will forgive him."
Hadith Referenceالمعجم الكبير للطبراني / باب الكاف / 16361