NET

18 If the Egyptians will not do so, they will get no rain—instead there will be the kind of plague that the Lord inflicts on any nations that do not go up to celebrate the Feast of Shelters.

Darby

18 And if the family of Egypt go not up, and come not, neither [shall it be] upon them; [there] shall be the plague, wherewith Jehovah will smite the nations that go not up to celebrate the feast of tabernacles.

KJV

18 And if the family of Egypt go not up, and come not, that [have] no [rain]; there shall be the plague, wherewith the LORD will smite the heathen that come not up to keep the feast of tabernacles.