It is enough - There is no need of any farther plague; I submit to the authority of Jehovah and will rebel no more.
Mighty thunderings - כלת אלהים koloth Elohim, voices of God; - that is, superlatively loud thunder. So mountains of God (Psalm 36:6) means exceeding high mountains. So a prince of God (Genesis 23:6) means a mighty prince. See a description of thunder, Psalm 29:3-8 : "The Voice Of The Lord is upon the waters: the God of glory thundereth; the Lord is upon many waters. The voice of the Lord is powerful; the voice of the Lord is full of majesty. The voice of the Lord breaketh the cedars. The voice of the Lord divideth the flames of fire. The voice of the Lord shaketh the wilderness," etc. The production of rain by the electric spark is alluded to in a very beautiful manner, Jeremiah 10:13 : When he uttereth his voice, there is a multitude of waters in the heavens. See Clarke's note on Genesis 7:11, and Genesis 8:1 (note).

Entreat the Lord, for it is enough,.... Hail, thunder, and lightning enough; or pray that this may be enough, and thought sufficient, and that there may be no more; or "entreat the Lord, and much" (l); pray, and pray much, pray earnestly and without intermission until the plague ceases:
that there be no more mighty thunderings and hail; or "voices of God" (m); for thunder is the voice of God, and these thunderings or voices were very loud, the claps were very terrible to hear, and the hail was very grievous and heavy, and the whole was very amazing and frightful, and the more to Pharaoh, who perhaps had never heard the voice of thunder, or seen an hail storm before, even a common one, these being rare in the land of Egypt:
and I will let you go, and ye shall stay no longer; go the three days' journey into the wilderness, directly and immediately; he would not put it off, on any account, and much less refuse to let them go at all, as he had often done.
(l) "orate multam", Rivet. (m) "voces Dei", Montanus, Drusius.