John Chrysostom

The strangers are Theudas, and Judas, and the false apostles who came after Christ. That He might not appear one of this number, He gives many marks of difference between Him and them. First, Christ brought men to Him by teaching them out of the Scriptures; they drew men from the Scriptures. Secondly, the obedience of the sheep; for men believed on Him, not only during His life, but after death: their followers ceased, as soon as they were gone.

Catena Aurea by Aquinas ↗

Theophylact of Ohrid

"A stranger they will not follow," because they do not know the voice of a stranger. And here, without a doubt, He hints at Theudas and Judas, whom the sheep did not follow, for few were deceived, and even those, after their death, fell away. But Christ, both during His life, and especially after His death, "the whole world went after Him" (John 12:19). He also hints at the antichrist, for he too will deceive only a few, and after his destruction will have no followers. …

Commentary on John ↗

Thomas Aquinas

The effect that the thief has is that the sheep do not follow him for very long, but only for a time; so he says, a stranger they will not follow, i.e., they do not follow a false and heretical teacher: "The children who are strangers have lied to me" (Ps 17:46). Thus Paul did not follow false teachers for long. But they will flee from him, because "Bad company ruins good morals" (1 Cor 15:33). …

Commentary on John ↗

Bonaventure

"But they do not follow a stranger, but flee from him," that is, an evil shepherd or a wolf, because they do not know the voice of strangers, that is, they do not approve of it. These strangers are false christs and false prophets and false apostles, of whom it is said in Second Corinthians eleven, that "they are deceitful workers, disguising themselves as apostles of Christ." These they do not follow: for they have been warned by their own shepherd; Matthew seven: "Beware of false prophets, who come to you in sheep's clothing, but …

Commentary on John, Chapter 10 ↗