John Chrysostom

And again He adds, "Neither be ye called guides, for one is your guide, even Christ;" and He said not, I. For like as above He said, "What think ye of Christ?" and He said not, "of me," so here too. But I should be glad to ask here, what they would say, who are repeatedly applying the term one, one, to the Father alone, to the rejection of the Only-begotten. Is the Father guide? All would declare it, and none would gainsay it. …

Homily on the Gospel of Matthew 72 ↗

Thomas Aquinas

Likewise, neither be ye called masters, for one is your master: Christ. Hence Christ attributes mastership to himself, because Christ is the Word; and therefore it belongs to him to teach, because no one teaches except through the Word. Likewise, he is master with respect to his human nature, because he was sent to teach; John 1:18: no man has seen God at any time. The only-begotten Son who is in the bosom of the Father, he has declared him. Likewise, ibid. 13:13: you call me master and Lord.

Commentary on Matthew ↗

Glossa Ordinaria

Because it was clear who was the Father of all, by this which was said, Which art in Heaven, He would teach them who was the Master of all, and therefore repeats the same command concerning a master, Neither be ye called masters; for one is your Master, even Christ.

Catena Aurea by Aquinas ↗