A narration from Imam Sadiq (a) which is cited in 'al-Kafi' says that one of his companions asked whether a believer may become discontented when his soul is being taken. He (s) replied:
"By Allah, No! When the angel of death comes to take his soul the believer shows restlessness and the angel says: 'O, Lover of Allah! Be not upset! By He Who has appointed Mohammad (s) to prophethood, I am more sympathetic to you than a kind father. Look carefully!' He looks carefully and sees Prophet Mohammad, Amir -al- Mo'mineen Ali, Fatimah, Hasan, Husain and other Imams from their descendants (a) .
The angel tells him to look and see that they (a) are all his friends. He opens his eyes and watches. A caller from Almighty Allah suddenly beckons and says: "O, you serene soul! Come back to your Lord well-pleased (with Him) and well-pleasing (Him) . So enter among My servants. And enter into My Garden ". At that moment there is nothing better and more beloved than that his soul separates from his body as soon as possible and moves unto his Lord.
Al-Kafi, vol. 3, Chapter Believers and the Departure of the Soul, Tradition 2.