Exodus 9:19

“Send therefore now, and gather thy cattle, and all that thou hast in the field, etc.] The servants that were at work there: this is said to denote both the certainty of the plague, and the terribleness of it, that all, both men and beast, would perish by it, if care was not taken to get them home; and also to show the wonderful clemency and mercy of God to such rebellious, hardened, and undeserving creatures, as Pharaoh and his people were; in the midst of wrath and judgment God remembers mercy: for upon every man and beast which shall be found in the field, and shall not be brought home; and there sheltered in houses, barns, and stables: the hail shall come down upon them, and they shall…”

“With the plague of hail begins the last series of plagues, which differ from the former both in their severity and their effects. Each produced a temporary, but real, change in Pharaoh’s feelings. Exodus 9:14 All my plagues - This applies to all the plagues which follow; the effect of each was foreseen and foretold. The words “at this time” point to a rapid and continuous succession of blows. The plagues which precede appear to have been spread over a considerable time; the first message of Moses was delivered after the early harvest of the year before, when the Israelites could gather stubble, i. e. in May and April: the second mission, when the plagues began, was probably toward the end of…”

“and gather: Hab 3:2 the hail: Exo 9:25 Exodus 9:20”

“The good advice to be given by Moses to the king, to secure the men and cattle that were in the field, i.e., to put them under shelter, which was followed by the God-fearing Egyptians ( Exo 9:21), was a sign of divine mercy, which would still rescue the hardened man and save him from destruction. Even in Pharaoh's case the possibility still existed of submission to the will of God; the hardening was not yet complete. But as he paid no heed to the word of the Lord, the predicted judgment was fulfilled ( Exo 9:22-26). "Jehovah gave voices" (קלת); called "voices of God" in Exo 9:28. This term is applied to the thunder (cf. Exo 19:16; Exo 20:18; Psa 29:3-9), as being the mightiest manifestation…”