Midrash sur Nahoum 1:5

The voice of the first (commandment) went forth, and the heavens and earth quaked thereat, and the waters and rivers fled, and the mountains and hills were moved, and all the trees fell prostrate, and the dead who were in Sheol revived, and stood on their feet till the end of all the generations, as it is said, "But with him that standeth here with us this day" (Deut. 29:15), and those (also) who in the future will be created, until the end of all the generations, there they stood with them at Mount Sinai, as it is said, "And also with him that is not here with us this day" (ibid.). The Israelites who were alive (then) fell upon their faces and died.