Sahih Muslim Book - 44, Hadith - 6378

حَدَّثَنَا أَبُو بَكْرِ بْنُ نَافِعٍ ، حَدَّثَنَا بَهْزٌ ، حَدَّثَنَا حَمَّادٌ ، أَخْبَرَنَا ثَابِتٌ ، عَنْ أَنَسٍ ، قَالَ : أَتَى عَلَيَّ رَسُولُ اللهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ ، وَأَنَا أَلْعَبُ مَعَ الْغِلْمَانِ ، قَالَ : فَسَلَّمَ عَلَيْنَا ، فَبَعَثَنِي إِلَى حَاجَةٍ ، فَأَبْطَأْتُ عَلَى أُمِّي ، فَلَمَّا جِئْتُ قَالَتْ : مَا حَبَسَكَ ؟ قُلْتُ بَعَثَنِي رَسُولُ اللهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ لِحَاجَةٍ ، قَالَتْ : مَا حَاجَتُهُ ؟ قُلْتُ : إِنَّهَا سِرٌّ ، قَالَتْ : لاَ تُحَدِّثَنَّ بِسِرِّ رَسُولِ اللهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ أَحَدًا. قَالَ أَنَسٌ : وَاللَّهِ لَوْ حَدَّثْتُ بِهِ أَحَدًا لَحَدَّثْتُكَ يَا ثَابِتُ.

It was narrated that Anas said: "The Messenger of Allah (s.a.w) came to me when I was playing with some other boys. He greeted us with Salam and sent me on an errand, and I was late in coming back to my mother. When I came she said: 'What kept you?' I said: 'The Messenger of Allah (s.a.w) sent me on an errand.' She said: 'What errand?' I said: 'It is a secret.' She said: 'Do not tell the secret of the Messenger of Allah (s.a.w) to anyone."' Anas said: "By Allah, if I were to have told it to anyone, I would have told it to you, O Thabit."