Hadithcore
Sahih al-Bukhari, 5190
sahih

Narrated 'Urwa:

Aisha said, "While the Ethiopians were playing with their small spears, Allah's Messenger (ﷺ) screened me behind him and I watched (that display) and kept on watching till I left on my own." So you may estimate of what age a little girl may listen to amusement.

حَدَّثَنَا عَبْدُ اللَّهِ بْنُ مُحَمَّدٍ، حَدَّثَنَا هِشَامٌ، أَخْبَرَنَا مَعْمَرٌ، عَنِ الزُّهْرِيِّ، عَنْ عُرْوَةَ، عَنْ عَائِشَةَ، قَالَتْ كَانَ الْحَبَشُ يَلْعَبُونَ بِحِرَابِهِمْ، فَسَتَرَنِي رَسُولُ اللَّهِ صلى الله عليه وسلم وَأَنَا أَنْظُرُ، فَمَا زِلْتُ أَنْظُرُ حَتَّى كُنْتُ أَنَا أَنْصَرِفُ فَاقْدُرُوا قَدْرَ الْجَارِيَةِ الْحَدِيثَةِ السِّنِّ تَسْمَعُ اللَّهْوَ‏.‏

References2 variants
In-Book Reference
Book 67, Hadith 124
USC-MSA web (English) reference
Vol. 7, Book 62, Hadith 118 (deprecated numbering scheme)