Yalkut Shimoni on Torah 208:12

"And the children of Israel journeyed from Ramses to Succoth" (Exodus 12:37). From Ramses to Succoth is a distance of forty parsangs. The voice of Moses traveled a distance of forty days' [journey]. And do not be astonished, for behold, it says (Exodus 9:8-9), "And the LORD said to Moses and to Aaron, Take to you handfuls of [soot] and so forth, and it shall become fine dust over all the land of Egypt." And behold, this is an argument from minor to major: if dust, whose nature it is not to travel, traveled a distance of forty days' [journey], how much more so for a voice, whose nature it is to travel, [it would carry] in the blink of an eye. The children of Israel journeyed from Ramses to Succoth, to fulfill what is said (Exodus 19:4), "And I bore you on eagles' wings."