John Gill Commentary Exodus 9:33

"And Moses went out of the city from Pharaoh, and spread abroad his hands unto Jehovah: and the thunders and hail ceased, and the rain was not poured upon the earth." — Exodus 9:33 (ASV)

And Moses went out of the city from Pharaoh
Into the field, where, being retired from company, he could freely, and without being disturbed, pray unto God:

and spread abroad his hands unto the Lord ;
denoting the spreading of cases before God, and expectation, hope, and readiness to receive favours from him:

and the thunder and hail ceased ;
immediately upon the entreaty of Moses; see the power and prevalence of prayer: a like instance we have in Elijah, (James 5:17James 5:18) and the rain was not poured upon the earth; so that there was rain as well as hail, which was restrained and entirely ceased.