John Chrysostom

And they said unto her, Thou art mad. But she constantly affirmed that it was even so. And they said, It is his angel. This is a truth, that each man has an Angel. It was from the time of night that they surmised this.

Homily on Acts 26 ↗

Theophylact of Ohrid

This is correct, because everyone has an Angel. With every believer in the Lord an Angel constantly abides, unless we drive him away by evil deeds, for just as smoke causes bees to depart and as a foul smell drives away doves, so the stinking and much-tear-causing sin distances the Angel from us. And they expected that it was an Angel, reasoning according to their situation, because it is said: "Where two or three are gathered in My name, there I am in the midst of them" (Matt. 18:20). …

Commentary on Acts ↗

Oecumenius

"It is his angel." From this it is clear that each one of us has an angel. But they expected this from the time. For he says, "Where two or three are gathered in my name, there am I among them." (Matt. 18:20) Where Christ is, there must be angels as well, and all the powers.

Commentary on Acts ↗

Bede

But they were saying, "It is his angel." That each of us has an angel is found both in the book of the Shepherd and in many places of the Holy Scriptures. For the Lord also speaks of the little ones: "Their angels always see the face of my Father" (Matt. XVIII). And Jacob speaks of himself: "The angel who redeemed me from all evil." And here the disciples believed that the angel of the apostle Peter had come.

Commentary on Acts ↗