Albert Barnes Commentary Isaiah 55:5

"Behold, thou shalt call a nation that thou knowest not; and a nation that knew not thee shall run unto thee, because of Jehovah thy God, and for the Holy One of Israel; for he hath glorified thee." — Isaiah 55:5 (ASV)

Behold, you shall call ... - This is evidently an address to the Messiah, and is a promise that the Gentiles should be called by him to the fellowship of the gospel.

That you do not know - The phrase ‘you do not know,’ means a nation that had not been regarded as his own people.

And nations that did not know you - The pagan nations that were strangers to you.

Shall run to you - Indicating the haste and anxiety which they would have to partake of the benefits of the true religion.

Because of the Lord your God - From respect to the God who had appointed the Messiah, and who had organized the Church.

For he has glorified you - (John 16:5). God had glorified him by appointing him to be the Messiah; and he would glorify him in the future triumphs of the gospel, in the day of judgment, and in the eternal splendors of heaven.