It is narrated from Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) was riding a camel on which a saddle-cloth had been fastened, and he (peace and blessings be upon him) said: "O Mu'adh!" I said: "Here I am at your service, O Messenger of Allah." He (peace and blessings be upon him) said: "Do you know what the right of Allah upon His servants is?" I said: "Allah and His Messenger know best." He (peace and blessings be upon him) said: "The right of Allah upon the servants is that they worship Him and do not associate anything with Him." Then he said: "Do you know what the right of the servants upon Allah is when they have done that?" I said: "Allah and His Messenger know best." He (peace and blessings be upon him) said: "Their right upon Him, when they have done that, is that He forgives them and admits them into Paradise."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17507