Sayyiduna Mu'adh bin Jabal (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings be upon him) passed by me while I was on a donkey, and he (peace and blessings be upon him) said: "O Mu'adh! Do you know what the right of Allah upon His servants is, and what the right of the servants upon Allah 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, and the right of the servants upon Allah, if they do that, is that He does not punish them."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17410