Charles Ellicott Commentary Isaiah 49:10

"They shall not hunger nor thirst; neither shall the heat nor sun smite them: for he that hath mercy on them will lead them, even by springs of water will he guide them." — Isaiah 49:10 (ASV)

Neither shall the heat ... —The word is the same as the parched ground of Isaiah 35:7, and stands, as there, for the mirage of the scorching desert.