The great hadith scholar and critic, Imam Abu Dawud (رحمه الله), who was one of the best students of Imamu Ahlis Sunnah, Ahmed ibn Hanbal (رحمه الله) said, I saw a young son of Imam Ahmed with a ta’weez around his neck on leather. 

[Masaail Imam Ahmed Narrated by Abu Dawud #1670 Pg.349]