Arabic text
عَنْ أَنَسِ بْنِ مَالِكٍ رَضِيَ اللَّهُ عَنْهُ قَالَ: مَا خَطَبَنَا نَبِيُّ اللهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ إِلَّا قَالَ: «لَا إِيمَانَ لِمَنْ لَا أَمَانَةَ لَهُ، وَلَا دِينَ لِمَنْ لَا عَهْدَ لَهُ».
Translation
Anas ibn Mālik (may Allah be pleased with him) reported: The Prophet of Allah (may Allah's peace and blessings be upon him) never addressed us except that he said: "He who has no integrity has no faith, and he who does not keep his covenant has no religion."
Explanation
Anas ibn Mālik (may Allah be pleased with him) informs that the Prophet (may Allah's peace and blessings be upon him) rarely delivered a sermon or gave advice without mentioning two things: First: There is no complete faith for he who harbors betrayal toward anyone regarding his wealth, person, or family. Second: There is no complete religion for he who betrays covenants and treaties and breaks them.
Source: HadeethEnc.com