Sahih Muslim 2482 a
Anas reported:
Allah's Messenger (ﷺ) came to me as I was playing with playmates. He greeted and sent me on an errand and I made delay in going to my mother. When I came to her she said: What detained you? I said: Allah's Messenger (ﷺ) sent me on an errand. She said: What was the purpose? I said: It is something secret. Therupon she said: Do not then divulge the secret of Allah's Messenger (ﷺ) to anyone. Anas said: By Allah, if I were to divulge it to anyone, then, O Thabit, I would have divulged it to you.
حَدَّثَنَا أَبُو بَكْرِ بْنُ نَافِعٍ، حَدَّثَنَا بَهْزٌ، حَدَّثَنَا حَمَّادٌ، أَخْبَرَنَا ثَابِتٌ، عَنْ أَنَسٍ، قَالَ
 أَتَى عَلَىَّ رَسُولُ اللَّهِ صلى الله عليه وسلم وَأَنَا أَلْعَبُ مَعَ الْغِلْمَانِ - قَالَ - فَسَلَّمَ عَلَيْنَا
 فَبَعَثَنِي إِلَى حَاجَةٍ فَأَبْطَأْتُ عَلَى أُمِّي فَلَمَّا جِئْتُ قَالَتْ مَا حَبَسَكَ قُلْتُ بَعَثَنِي رَسُولُ اللَّهِ
 صلى الله عليه وسلم لِحَاجَةٍ ‏.‏ قَالَتْ مَا حَاجَتُهُ قُلْتُ إِنَّهَا سِرٌّ ‏.‏ قَالَتْ لاَ تُحَدِّثَنَّ بِسِرِّ رَسُولِ
 اللَّهِ صلى الله عليه وسلم أَحَدًا ‏.‏ قَالَ أَنَسٌ وَاللَّهِ لَوْ حَدَّثْتُ بِهِ أَحَدًا لَحَدَّثْتُكَ يَا ثَابِتُ ‏.‏