Cyril of Alexandria

And all flesh did see the salvation of God, even of the Father: for He sent the Son to be our Saviour. And in these words by "flesh," man generally is to be understood, that is, the whole human race. For thus all flesh shall see the salvation of God: no longer Israel only, but all flesh. For the gentleness of the Saviour and Lord of all is not limited, nor did He save one nation merely, but rather embraced within His net the whole world, and has illuminated all who were in darkness. …

Commentary on the Gospel of Luke, Sermon VI ↗

Theophylact of Ohrid

"Every flesh shall see," it is said, "the salvation of God" — not only the Jews and proselytes, but "every flesh," for the Gospel has been carried throughout all the earth. One could say much more besides, but for the sake of greater clarity, let this suffice.

Commentary on Luke ↗

Augustine of Hippo

The expression of Scripture, "And all flesh shall see the salvation of God," may without difficulty be understood as if it were said, "And every man shall see the Christ of God." And He certainly was seen in the body, and shall be seen in the body when He judges quick and dead. …

City of God 22.29 ↗

Gregory the Dialogist

There follows: "And all flesh shall see the salvation of God." Because by "all flesh" is meant every person, not every person was able to see the salvation of God, namely Christ, in this life. Where then does the prophet direct the eye of prophecy in this statement except to the day of the last judgment? …

Forty Gospel Homilies, Homily 20 ↗

Bede

And all flesh shall see the salvation of God. Because "all flesh" is understood as every human being, but not every human being could see Christ, the salvation of God, in this life. So where does the prophet direct the prophetic eye in this sentence if not toward the day of the final judgment? …

On the Gospel of Luke ↗