Theophylact of Ohrid

And the "veil" of the temple "is torn." By this the Lord shows that the Holy of Holies will no longer be inaccessible, but will be given over to the Romans, trampled and defiled. Or again, He shows that the veil is torn that separated us from the saints living in the heavens, that is, enmity and sin. For this constituted a great barrier dividing us from those living there. He shows at the same time that He was not crucified out of powerlessness. For He who performed such a sign could have torn them apart and destroyed them.

Commentary on Luke ↗

Augustine of Hippo

This darkening of the sun it is quite plain did not happen in the regular and fixed course of the heavenly bodies, because it was then the Passover, which is always celebrated at the full moon. But a regular eclipse of the sun does not take place except at new moon.

Catena Aurea by Aquinas ↗

Ambrose of Milan

The veil also is rent, by which is declared the division of the two people, and the profanation of the synagogue. The old veil is rent that the Church may hang up the new veils of faith. The covering of the synagogue is drawn up, that we may behold with the eyes of the mind the inward mysteries of religion now revealed to us. It took place also at that time when every mystery of Christ's assumed mortality was fulfilled, and His immortality alone remained; as it follows, And when Jesus had cried with a loud voice, he said.

Catena Aurea by Aquinas ↗

Bede

And the veil of the temple was torn in two. This happened as the Lord expired, as Matthew and Mark attest, but Luke relates it in advance. For, wishing to add miracle to miracle, when he had said "The sun was darkened," he immediately considered it appropriate to add: "And the veil of the temple was torn in two." The veil of the temple is torn, so that the secrets of the covenant and all the sacraments of the law, which were previously covered, may appear and be accessible to the nations. …

On the Gospel of Luke ↗