“When Allah will raise the believer out of his grave, another presence will also come out with him and walk ahead of him. Whenever the believer will come across any terror of the Day of Resurrection, the presence will console him saying, ‘Do not worry or be saddened…‘ at which the believer will ask, ‘Who are you?‘ to which it will reply, ‘I am the happiness that you used to bring upon your fellow believer.’

– Imam Jafar ibne Muhammad as-Sadiq (as)

(Reference: Al-Kafi, pg. 190, hadith no. 8)