But thou art the same - הוא ואתה veattah Hu, but thou art He, that is, The Eternal; and, consequently, he who only has immortality.
Thy years shall have no end - יתמו לא lo yittammu, "they shall not be completed." Every thing has its revolution - its conception, growth, perfection, decay, dissolution, and death, or corruption. It may be said that regeneration restores all these substances; and so it does in a measure, but not without deterioration. The breed of animals, as well as vegetables, wears out; but God's eternal round has no completion. I repeat it, - what is necessarily eternal is unchangeable and imperishable; all created beings are perishable and mutable, because not eternal. God alone is eternal; therefore God alone is imperishable and immutable.
Of old - See this passage fully explained in the notes at Hebrews 1:10-12. In the beginning; at the first. The phrase used here means literally “to the face;” then, “before” in the order of time. It means here, long ago; of olden time; at the beginning. The meaning is, that the years of God had stretched through all the generations of people, and all the changes which had occurred upon the earth; that at the very beginning he existed, and that he would continue to exist to the very close, unchangeably the same.