Thomas Aquinas, on Heb 13:8

“Jesus Christ, yesterday, and today; and the same for ever.”

“He continues: Jesus Christ, yesterday, and today: and the same forever. According to a Gloss this is the way this section is introduced. For he had said before, I will not leave you or forsake you. But they could say: The one to whom this was said can well trust in God's help, but not we to whom it was not spoken. But the Apostle rejects this, saying that Christ remains forever; hence, he says, Jesus Christ, yesterday, and today: and the same forever. Or it can be referred to what he had just said, namely, that they should imitate the apostles. They could say that the case is not the same, because they were instructed by Christ and served Him, but we not so. Therefore, the Apostle says that Christ remains; hence, he says that we should serve Him. And so he says, Jesus Christ, yesterday, namely, in the time of the first apostles, and today, namely, in their time, and the same forever: 'I am with you all days even to the consummation of the world' (Mt. 28:20); 'Says the Lord, who is, and who was, and who is to come, the Almighty' (Rev. 1:8); 'But you are always the selfsame, and your years shall not fail' (Ps. 101:28). In these words he shows the eternity of Christ.”

Imported from an open dataset — not yet checked against the printed edition.