John Calvin 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)

They shall not hunger or thirst. He confirms what was said in the previous verse, that there is food in the hand of God, so that the Jews will not lack provisions for their journey. Nor can it be doubted that he reminds them that when their fathers were threatened with death in the wilderness through a scarcity of bread and of every kind of food, God gave them daily, for forty years, manna from heaven (Exodus 16:35).

Likewise, when he immediately afterwards speaks of a shadow against the heat of the sun, he alludes to the history related by Moses about “the pillar of a cloud,” by which God protected his people from being scorched by the burning rays of the sun (Exodus 13:21). We have said that it is customary for the prophets to mention the departure of the people out of Egypt, whenever they intend to demonstrate the kindness of God, either publicly towards all or privately towards any individual.

By the fountains of waters. He likewise alludes to those waters which flowed from the rock (Exodus 17:6), when the people had nearly perished from thirst; for those occurrences did not take place at the deliverance from Babylon, but, by mentioning past benefits, the Prophet magnifies the power of God in securing the safety of the Church.