The Book of Faith ( Sahih Muslim No.143).

 حَدَّثَنَا هَدَّابُ بْنُ خَالِدٍ الْأَزْدِيُّ، حَدَّثَنَا هَمَّامٌ، حَدَّثَنَا قَتَادَةُ، حَدَّثَنَا أَنَسُ بْنُ مَالِكٍ، عَنْ مُعَاذِ بْنِ جَبَلٍ، قَالَ: كُنْتُ رِدْفَ النَّبِيِّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ لَيْسَ بَيْنِي وَبَيْنَهُ إِلَّا مُؤْخِرَةُ الرَّحْلِ، فَقَالَ: «يَا مُعَاذُ بْنَ جَبَلٍ»، قُلْتُ: لَبَّيْكَ رَسُولَ اللهِ، وَسَعْدَيْكَ، ثُمَّ سَارَ سَاعَةً، ثُمَّ قَالَ: «يَا مُعَاذُ بْنَ جَبَلٍ» قُلْتُ: لَبَّيْكَ رَسُولَ اللهِ وَسَعْدَيْكَ، ثُمَّ سَارَ سَاعَةً، ثُمَّ قَالَ: «يَا مُعَاذُ بْنَ جَبَلٍ» قُلْتُ: لَبَّيْكَ رَسُولَ اللهِ وَسَعْدَيْكَ، قَالَ: «هَلْ تَدْرِي مَا حَقُّ اللهِ عَلَى الْعِبَادِ؟» قَالَ: قُلْتُ: اللهُ وَرَسُولُهُ أَعْلَمُ، قَالَ: «فَإِنَّ حَقُّ اللهِ عَلَى الْعِبَادِ أَنْ يَعْبُدُوهُ، وَلَا يُشْرِكُوا بِهِ شَيْئًا»، ثُمَّ سَارَ سَاعَةً، ثُمَّ قَالَ: «يَا مُعَاذَ بْنَ جَبَلٍ» قُلْتُ: لَبَّيْكَ رَسُولَ اللهِ، وَسَعْدَيْكَ، قَالَ: «هَلْ تَدْرِي مَا حَقُّ الْعِبَادِ عَلَى اللهِ إِذَا فَعَلُوا ذَلِكَ؟» قَالَ: قُلْتُ: اللهُ وَرَسُولُهُ أَعْلَمُ، قَالَ: «أَنْ لَا يُعَذِّبَهُمْ»

 It is narrated on the authority of Mu'adh b. Jabal:

I was riding behind the Prophet ( ‌صلی ‌اللہ ‌علیہ ‌وسلم ‌ ) and there was nothing between him and me but the rear part of the saddle, when he said: Mu'adh b. Jabal: To which I replied: At your beck and call, and at your pleasure, Messenger of Allah! He moved along for a few minutes, when again he said: Mu'adh b. Jabal: To which I replied: At your beck and call, and at your pleasure, Messenger of Allah! He then again moved along for a few minutes and said: Mu'adh b. Jabal: To which I replied. At your beck and call, and at your pleasure. Messenger of Allah He, (the Holy Prophet) said: Do you know what right has Allah upon His servants? I said: Allah and His Messenger know best. He (the Holy Prophet) said: Verily the right of Allah over His servants is that they should worship Him, not associating anything with Him. He (the Holy Prophet) with Mu'adh behind him, moved along for a few minutes and said: Mu'adh b. Jabal: To which I replied: At your beck and call, and at your pleasure, Messenger of Allah! He (the Holy Prophet) said: Do you know what rights have servants upon Allah in case they do it (i. e. they worship Allah without associating anything with Him)? I (Mu'adh b. Jabal) replied: Allah and His Messenger know best. (Upon this) he (the Holy Prophet) remarked: That He would not torment them (with the fire of Hell).

 The Book of Faith ( Sahih Muslim No. 143)