Musnad Ahmad 4207

It was narrated from Ibn Mas'ood (رضي الله عنه) that The Prophet (ﷺ) recited (Soorat) an-Najm and prostrated in it, and those who were with him prostrated, except an old man who took a handful of pebbles or dust and did like this - and he put it on his forehead. 'Abdullah said: And I saw him slain as a kafir.