Albert Barnes Commentary Isaiah 40:29

"He giveth power to the faint; and to him that hath no might he increaseth strength." — Isaiah 40:29 (ASV)

He giveth power to the faint - To his weak and feeble people. This is one of his attributes; and his people, therefore, should put their trust in him, and look to him for aid (Compare to 2 Corinthians 12:9).

The design of this verse is to give consolation to the afflicted and down-trodden people in Babylon, by recalling to their minds the truth that it was one of the characteristics of God that he ministered strength to those who were conscious of their own feebleness, and who looked to him for support. It is a truth, however, as applicable to us as to them, a truth inestimably precious to those who feel that they are weak and feeble, and who look to God for aid.