Musnad Abu Ya'la al-Mawsili 160:55

Muhammad ibn al-Muthanna narrated to us, Ma'di ibn Sulayman Abu Sulayman, the owner of the food, narrated to us, from Ibn 'Ajlan, from his father, from Abu Hurayrah, who said: The Messenger of Allah (ﷺ) said: "Is it expected that one of you will take some sheep and stay at the top of a mountain, a mile or two from Medina, and then Friday comes and he does not attend the Friday prayer, then Friday comes and he does not attend the Friday prayer, until a seal is placed upon his heart, and he becomes one of the heedless."