Albert Barnes Commentary Isaiah 40:28

"Hast thou not known? hast thou not heard? The everlasting God, Jehovah, the Creator of the ends of the earth, fainteth not, neither is weary; there is no searching of his understanding." — Isaiah 40:28 (ASV)

Have you not known? – This is the language of the prophet reproving them for complaining of being forsaken and assuring them that God was faithful to His promises. This argument of the prophet, which continues to the end of the chapter, comprises the main scope of the chapter, which is to lead them to put confidence in God and to believe that He was able and willing to deliver them. The phrase Have you not known? refers to the fact that the Jewish people had an abundant opportunity to learn, in their history and from their fathers, the true character of God and His entire ability to save them.

No people had had so much light on this subject, and now that they were in trial, they ought to recall their former knowledge of His character and remember His faithful dealings with them and their fathers. It is well for the people of God in times of calamity and trial to recall His former dealings with His church. That history will furnish abundant sources of consolation and abundant assurances that their interests are safe in His hands.

Have you not heard? – From the traditions of the fathers; the instruction which you have received from ancient times. A large part of the knowledge of the Jews was traditional, and these attributes of God, as a faithful God, had, no doubt, constituted an important part of the knowledge that had thus been communicated to them.

The everlasting God – The God who has existed from eternity, unlike pagan idols. If He existed from eternity, He would be unchangeable, and His purposes could not fail.

The Creator of the ends of the earth – The phrase the ends of the earth means the same as the earth itself. The earth is sometimes spoken of as a vast plain having limits or boundaries . It is probable that this was the prevailing idea among the ancients (1 Samuel 2:10; Psalms 19:6; Psalms 22:27; Psalms 48:10; Psalms 65:5; Psalms 67:7; Psalms 98:3; Isaiah 43:6; Isaiah 45:22; Isaiah 52:10). The argument here is that He who has formed the earth could not be exhausted or weary in so small a work as protecting His people.

Faints not – Is not fatigued or exhausted. That God, who has formed and sustained all things, is not exhausted in His powers, but is still able to defend and guard His people.

There is no searching of His understanding – The God who made all things must be infinitely wise. There is proof of boundless skill in the works of His hands, and it is impossible for the finite mind to fully and adequately search out all the proofs of His wisdom and skill. Humans can see only a part—a small part—while the vast ocean, the boundless deep of His wisdom, lies still unexplored. This thought is beautifully expressed by Zophar in Job 11:7-9:

Can you by searching find out God?
Can you find out the Almighty to perfection?
It is as high as heaven;
What can you do?
Deeper than hell;
What can you know?
Its measure is longer than the earth,
And broader than the sea.

The argument here is that the God who has made all things must be intimately acquainted with the needs of His people. They had, therefore, no reason to complain that their way was hidden from the Lord and their cause passed over by Him. Perhaps, also, it is implied that as His understanding was vast, they ought not to expect to be able to comprehend the reason for all His actions, but should expect that there would be much that was mysterious and unsearchable. The reasons for His actions are often hidden from His people, and their consolation is to be found in the assurance that He is infinitely wise, and that He who rules over the universe must know what is best and cannot err.