Musannaf Ibn Abi Shayba 27:678

Ibn Fudayl narrated to us, from ‘Ata’, from Mujahid, from Ibn ‘Umar, who said: "The Throne shook out of love for meeting Allah, Sa‘d." He said: "It only means the bed (bier)." He said: "Its wooden frames cracked." He said: "The Messenger of Allah (peace and blessings of Allah be upon him) entered his grave and was delayed. When he came out, it was said: 'O Messenger of Allah, what delayed you?' He said: 'Sa‘d was squeezed in the grave with a squeeze, so I supplicated to Allah to relieve him of it.'"