Ibn Abee Ya’laa reports in his Tabaqaatul-Hanaabilah [with the verification and checking of Fawwaaz Ahmad Zumarlee], 1/163-167, from Sulaymaan ibn ‘Abdullaah as-Sijzee (who said), “I came to the door of al-Mu’tasim and saw that the people had crowded together at his door, as if it was the day of ‘Eed. I entered the place and saw a spread out carpet and a chair that had been thrown on the floor. I stood facing the chair and whilst I was standing, al-Mu’tasim approached and sat on the chair. He removed his shoes from his feet and placed one foot on top of the other. Then he said, ‘Let Imaam Ahmad be present,’ so he was brought out in his presence. After Imaam Ahmad had stood in front of him and greeted him he (al-Mu’tasim) said, ‘O Ahmad, speak and do not be afraid.’ So Imaam Ahmad, said, “By Allaah, O Ameerul-Mu’mineen, I have just entered upon you and there is not a seed’s weight of anxiety in my heart.”
Al-Mu’tasim said to him, ‘What do you say about the Qur’aan?’
He said, “The speech of Allaah, eternal, not created. Allaah, the Mighty and Majestic, said:
And if anyone of the Mushrikeen seeks your protection, then grant him protection, so that he may hear the Word of Allaah (the Qur’aan). [Soorah at-Tawbah (9):6]
So he said, ‘Do you have a proof other than this?’
Imaam Ahmad replied, “Yes, O Ameerul-Mu’mineen, the saying of Allaah, the Mighty and Majestic:
Ar-Rahmaan. He taught you (mankind) the Qur’aan. [Soorah ar-Rahmaan (55):1-2]
And He did not say: ‘Ar-Rahmaan. He created the Qur’aan.’ And His saying, the Mighty and Majestic:
Yaaseen. By the Qur’aan, full of wisdom. [Soorah Yaa Seen (36):1-2]
And He did not say: ‘Yaa Seen. By the Qur’aan (that is) created.’
So al-Mu’tasim said, ‘Imprison him.’ So he was imprisoned and the people dispersed. When I arose (the next morning) I made my way to the door (of al-Mu’tasim) and the people were entering, so I entered along with them. Al-Mu’tasim approached and sat on his chair and said, ‘Bring Ahmad ibn Hanbal,’ and so he was brought. When he stood in front of him, al-Mu’tasim said to him, ‘How were you in your cell yesterday, O Ahmad?’
Imaam Ahmad said, “In goodness, and all praises are due to Allaah, except that in my cell, O Ameerul-Mu’mineen, I saw something amazing.” He said to him, “And what did you see?” So he replied, “I arose in the middle of the night, performed ablution for the prayer and prayed two rak’ahs. In one rak’ah I recited: ‘Al-Hamdulillaah…’ and ‘Qul-A’oodhu bi-Rabbin-Naas,’ and in the second rak’ah: “Alhamdulillaah…’ and ‘Qul-A’oodhu bi-Rabbil-Falaq.’ Then I sat down, read the tashahhud and gave salutation (to my right and left). Then I stood (again), made the takbeer and recited: ‘Alhamdulillaah…’ and then I desired to read: ‘Qul-Huwallaahu-Ahad,’ and I was not able. I tried hard to read something else from the Qur’aan and I was not able. Then I stretched my eyes to the corner of the prison and (behold) I saw the Qur’aan laid out (on the floor), dead. So I washed it and shrouded it, then prayed over it and buried it.”
So al-Mu’tasim said, ‘Woe be to you, O Ahmad, and does the Qur’aan die!?’ So Ahmad said to him, “Well, that is what you say – that it is created. And everything that is created dies.” Al-Mu’tasim said, ‘Ahmad has subdued us, Ahmad has subdued us.’
Source: The Foundations of the Sunnah by the revered Imaam, the Scholar, the Teacher, the Reviver of the Sunnah, the Subduer of Innovation, Ahmad ibn Muhammad ibn Hanbal (d. 241H), English Translation Additional Footnotes and Chapters by Amjad ibn Muhammad Rafiq, Salafi Publications, Second Edition: Muharram 1424/March 2003, pp.91-93.
It sounds like Imaam Ahmad was telling a story to get an effect. Subhanallah! Did he really bury the Qur’an?
Allah knows best. It is worth noting though that during the Mihnah (the trial or inquisition concerning the claim/belief that the Qur’an is created) many narrations were reported, and this one in particular was to demonstrate a strong argument to subdue the innovative belief of the astray Jahmiyyah that the Qur’an is created.