مَن تَعَلَّمَ فی شَبابِهِ کانَ بِمَنْزِلَةِ الوَشْمِ فی الحَجَرِ، وَمَن تَعَلَّمَ وَهُوَ کبَیرٌ کانَ بِمَنْزِلَةِ الکِتابِ عَلَی وَجْهِ الماءِ. Who was learns in his youth is like a engraving on a stone, and he who was learns in his adulthood is like writing on the surface of water.
Al-Nadawar Ravandi, page 132, hadith 169
Rasul Allah Hazrat Muhammad (Peace and blessings of Allah be upon him and his progeny)Hadith