Augustine of Hippo

But whatever may be decided concerning these brethren, yet concerning the holy Virgin Mary, (for the honour of Christ,) when sin in her is in question, I would not have it brought into doubt. For from this only we might know that more abundant grace was conferred upon her that she should overcome sin on all sides, because she merited to conceive and bring forth Him Who it is clear had no sin. It follows; Then said one unto him, Behold, thy mother and thy brethren stand without seeking thee.

Catena Aurea by Aquinas ↗

Jerome

He that delivers this message, seems to me not to do it casually and without meaning, but as setting a snare for Him, whether He would prefer flesh and blood to the spiritual work; and thus the Lord refused to go out, not because He disowned His mother and His brethren, but that He might confound him that had laid this snare for Him.

Catena Aurea by Aquinas ↗

Thomas Aquinas

Someone told him, "Your mother and brothers are standing outside, asking to speak to you." Why he said this and the need for it are explained in Luke (8:19), namely, there was such a crowd that they could not reach him. Mystically, the synagogue is signified by the mother; hence Song of Songs (3:11): "Go forth and behold king Solomon with the crown with which his mother crowned him." And brothers, i.e., the Jews, who stood outside and abandoned Christ: "My brothers have abandoned me" (Jb 6:15). …

Commentary on Matthew ↗