Reference: Siyar A’laam an-Nubalaa – Volume 7, Page 5
Ma’mar ibn Raashid said:
I heard (sought knowledge) from Qataadah when I was 14 years old, and there is nothing which I heard during those years except that it [remains with me] as if written in my heart.
 Popular Arab saying:
الحِفْظُ فِي الصِّغَرِ كَالنَّقْشِ عَلَى الحَجَرِ
Memorising when one is young is like etching [something] on stone.