וְקוֹיֵ֤ יְהוָה֙ יַחֲלִ֣יפוּ כֹ֔חַ יַעֲל֥וּ אֵ֖בֶר כַּנְּשָׁרִ֑ים יָר֙וּצוּ֙ וְלֹ֣א יִיגָ֔עוּ יֵלְכ֖וּ וְלֹ֥א יִיעָֽפוּ׃ (פ)
但仰望永恆者的人必重新得力；他們必如鷹展翅上騰；他們奔跑卻不困倦，行走卻不疲乏。
Tze'enah Ure'enah
“Those who trust in the Lord will renew their strength, etc.” [40:31]. Israel trusts in God that they will have good strength. They will exchange their strength, just like an eagle every ten years grows new feathers, until a hundred years. In the same way, Israel will be strong and they will not be tired.5Radak, Isaiah, 40:31.
Ibn Ezra
יחליפו כח Shall renew their strength. Before one power is exhausted, the other is prepared for them by the Almighty. Comp. if it be cut down, (יחליף) it will sprout again (Job. 14:7). In Arabic this word has a similar meaning.64خَلَفَ Successor alicujus fuit; خَلِيفَةٌ Khalif. (Freytag, Lex. Arab. Lat.)