Cyril of Alexandria

The Lord joins one miracle upon another. In the Former instance He came indeed when called for, but in this He came self-invited; as it is said, And it came to pass the day after that he went into a city called Nain.

Catena Aurea by Aquinas ↗

Bede

And his disciples were going with him, and a great crowd. As he drew near to the gate of the city, behold, a dead man was being carried out, the only son of his mother. This deceased, who was being borne out of the gate of the city with many looking on, represents a man lulled by the lethal funeral of sins, and this same death of the soul, no longer hidden in the chamber of the heart, but made known to many by the indication of speech or action, as if disclosed through the gates of his city. …

On the Gospel of Luke ↗

Bonaventure

According to the spiritual understanding, note that a threefold state is designated in the course of this miracle, namely the state of justice in the Lord's company; the state of injustice in the dead young man; and the state of penance in the same one raised to life. The state of justice is designated in Christ and his company. For the state of the just is threefold, namely of contemplation, prelacy, and action. …

Commentary on Luke, Chapter 7 ↗