Sayyiduna Ibn Abbas (may Allah be pleased with them both) said concerning this saying of Allah Almighty, "And if there were a Qur'an by which the mountains were set in motion, or the earth were cut asunder, or the dead were made to speak" [Al-Ra'd: 31]: The polytheists said to the Prophet (peace and blessings be upon him): "If it is as you say, then show us our earliest elders who have died so that we may speak to them, and open up for us these mountains, the mountains of Makkah that have hemmed us in." So this verse was revealed: "And if there were a Qur'an by which the mountains were set in motion, or the earth were cut asunder, or the dead were made to speak" [Al-Ra'd: 31].
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 12563