Sahih al-Bukhari 6267
Narrated Mu`adh:
While I was a companion rider with the Prophet (ﷺ) he said, "O Mu`adh!" I replied, "Labbaik wa 
Sa`daik." He repeated this call three times and then said, "Do you know what Allah's Right on His 
slaves is?" I replied, "No." He said, Allah's Right on His slaves is that they should worship Him 
(Alone) and should not join partners in worship with Him." He said, "O Mu`adh!" I replied, "Labbaik 
wa Sa`daik." He said, "Do you know what the right of (Allah's) salves on Allah is, if they do that 
(worship Him Alone and join none in His worship)? It is that He will not punish them."

(another chain through Mu'adh)
حَدَّثَنَا مُوسَى بْنُ إِسْمَاعِيلَ، حَدَّثَنَا هَمَّامٌ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، عَنْ مُعَاذٍ، قَالَ أَنَا رَدِيفُ النَّبِيِّ، صلى الله عليه وسلم فَقَالَ ‏"‏ يَا مُعَاذُ ‏"‏‏.‏ قُلْتُ لَبَّيْكَ وَسَعْدَيْكَ‏.‏ ثُمَّ قَالَ مِثْلَهُ ثَلاَثًا ‏"‏ هَلْ تَدْرِي مَا حَقُّ اللَّهِ عَلَى الْعِبَادِ أَنْ يَعْبُدُوهُ وَلاَ يُشْرِكُوا بِهِ شَيْئًا ‏"‏‏.‏ ثُمَّ سَارَ سَاعَةً فَقَالَ ‏"‏ يَا مُعَاذُ ‏"‏‏.‏ قُلْتُ لَبَّيْكَ وَسَعْدَيْكَ‏.‏ قَالَ ‏"‏ هَلْ تَدْرِي مَا حَقُّ الْعِبَادِ عَلَى اللَّهِ إِذَا فَعَلُوا ذَلِكَ أَنْ لاَ يُعَذِّبَهُمْ ‏"‏‏.‏     
حَدَّثَنَا هُدْبَةُ، حَدَّثَنَا هَمَّامٌ، حَدَّثَنَا قَتَادَةُ، عَنْ أَنَسٍ، عَنْ مُعَاذٍ، بِهَذَا‏.‏