Theophylact of Ohrid

And there followed Him great multitudes of people from Galilee, and from Decapolis, and from Jerusalem, and from Judea, and from beyond the Jordan.

Commentary on Matthew ↗

Thomas Aquinas

Then is mentioned the third effect, namely, the devotion of the followers; hence, he says Great crowds followed him. "Awake, O my God; you have appointed a judgment. Let the assembly of peoples be gathered about you" (Ps 7:6). But it should be noted that people follow him in different ways: because some with an interest in health, i.e., spiritual; hence, "having left all things, they followed him" (Mt 4:22); "Lo, we have left all things and followed you" (Mt 19:27). …

Commentary on Matthew ↗

Remigius of Rheims

Or, they follow the Lord from Galilee, that is, from the unstable world; from Decapolis, (the country of ten towns,) signifying those who break the Ten Commandments; and from Jerusalem, because before it was preserved unhurt in peace; and from Jordan, that is, from the confession of the Devil; and from beyond Jordan, they who were first planted in paganism, but passing the water of Baptism came to Christ.

Catena Aurea by Aquinas ↗

Glossa Ordinaria

The crowds that follow the Lord, are they of the Church, which is spiritually designated by Galilee, passing to virtuousness; Decapolis is he who keeps the Ten Commandments; Jerusalem and Judæa, he who is enlightened by the vision of peace and confession; and beyond Jordan, he who having passed the waters of Baptism enters the land of promise.

Catena Aurea by Aquinas ↗