Exodus 10:21
And the LORD said unto Moses, Stretch out thine hand toward heaven, that there may be darkness over the land of Egypt, even darkness which may be felt.
And the Lord said unto Moses,.... About the eleventh day of the month Abib:
Stretch out thine hand toward heaven; where the luminaries are, and from whence light comes:
that there may be darkness over the land of Egypt, even darkness which may be felt; that is, what caused it, the gross vapours and thick fogs; for otherwise darkness itself, being a privation of light, cannot be felt: Onkelos paraphrases it,
"after that the darkness of the night is removed;''
so Jonathan; that it might appear to be different from that, and be much grosser.