438 – Ishaq ibn Ibrahim narrated to us; Abu al-Mughira al-Nadr ibn Ismaʿil narrated to us. He said: I heard Ibn Abi Layla say, “A boy’s front teeth fall out at seven, he experiences his first nocturnal emission at fourteen, his height stops increasing at twenty-one, and his intellect is perfected at twenty-eight; thereafter he gains no further intelligence except through experience.”