Sunan Ibn Majah 710
سنن ابن ماجه#710Da'ifAbdur-Rahman bin Sa'd bin 'Ammar bin Sa'd, who was the Mu'adh-dhin of the Messenger of Allah narrated from his grandfather, that:The Messenger of Allah commanded Bilal to put his fingers in his ears when calling the Adhan, and he said: "It makes the voice louder
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Al-AlbaniDaif
Muhammad Fouad Abd al-BaqiDaif
Zubair Ali ZaiDaif
In-book reference: 3:5