Musnad Ahmad 33:912

Ya'qub narrated to us, my father narrated to us, from Ibn Ishaq, Mu'adh ibn Rifa'ah narrated to me, from Mahmud ibn 'Abd al-Rahman ibn 'Amr ibn al-Jamuh, from Jabir ibn 'Abd Allah, who said: When Sa'd was buried, and we were with the Messenger of Allah, peace and blessings of Allah be upon him, the Messenger of Allah, peace and blessings of Allah be upon him, glorified Allah (said *SubhanAllah*), and the people glorified Allah with him for a long time. Then he magnified Allah (said *Allahu Akbar*), and the people magnified Allah. Then they said: "O Messenger of Allah, why did you glorify Allah?" He said: "The grave of this righteous man tightened upon him, until Allah relieved him of it."