Zarara b. A'yun has narrated, saying: "I visited Abu 'Abd Allah (al-Sadiq), peace be on him. There was with him the master of his children Abu al-Hasan Musa, and there was in his assembly a corpse covered with a garment. Abu 'Abd Allah (al-Sadiq), peace be on him, ordered me to bring him Dawud al-Raqqi, Hamran, and Abu Baseer. I went out to bring them and came across al-Mufaddal b. 'Amr, who was heading for the Imam. (Meanwhile) I saw the people going to the house of the Imam. I quickly went and brought the people to him. When they had the honor of meeting him, he, peace be on him, turned to Dawud al-Raqqi and said to him: 'Uncover Isma'il's face.' He uncovered his face and he was a motionless corpse. He, peace be on him, asked Dawud al-Raqqi: 'Dawud, is he alive or dead?'
"'My master, he is dead.'"
He showed him to all those who attended his assembly to make them bear witness to his death; he asked them to acknowledge and admit his death. He did that to refute the claims of some Shi'ites who maintained that Isma'il would be the Imam after his father, for he was righteous and abundantly knowledgeable. He, peace be on him, wanted to return them to reason and correctness and to tell them that the Imam after him was his son Musa. Then he ordered Isma'il to be prepared for burial. He was washed and shrouded. Then the Imam ordered al-Mufaddal b. 'Amr to uncover Isma'il's face again that the people might see him and be sure of his death and that they would have no doubt about that. After that he wanted to increase them in certainty and to remove doubt from them, so he turned to all his companions and asked them: "Is he alive or dead?"
They all confessed his death, so the Imam, peace be on him, raised his hands towards the heaven, saying: "O Allah, bear witness, for surely those who say untrue things will have doubt about him. They desire to put out the light of Allah-he pointed to his son Musa- with their mouths, but Allah will perfect His light, though the unbelievers may be averse. Then the Imam ordered Isma'il to be buried in his final resting place. After he had laid him to rest in the narrow space within the grave and poured the earth over him, he turned to his companions to remove doubts and suspicions from them, asking: "Who is the one who is dead, shrouded, perfumed, and buried in the grave?"
"He is Isma'il," they all said.
"O Allah, bear witness!" Then he took his son by the hand and said: "He will be the truth; the truth will be with him and (issue) from him till Allah inherits the earth and those who are on it." Bihar al-Anwar, vol. 11, p. 237.