Sahih Bukhari
Wedlock, Marriage (Nikaah)
Volume: 007 / Book Number: 062 / Hadith Number: 118
Narrated 'Ursa:
Aisha said, "While the Ethiopians were playing with their small spears, Allah's Apostle 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.