John Chrysostom

"I therefore so run, as not uncertainly." Thus having shamed them from those that are without, he next brings forward himself also, which kind of thing is a most excellent method of teaching: and accordingly we find him every where doing so. But what is, "not uncertainly?" "Looking to some mark," saith he, "not at random and in vain, as ye do. For what profit have ye of entering into idol-temples, and exhibiting for-sooth that perfectness? None. But not such am I, but all things whatsoever I do, I do for the salvation of my neighbor. …

Homily on 1 Corinthians 23 ↗

Theophylact of Ohrid

What does "as uncertainly" mean? That I do everything with purpose—when I cut off, when I trim—and I do nothing without thought and without purpose, as you do. For what purpose is there in eating food offered to idols, when others perish because of it? Absolutely none. Therefore, doing this without a reasonable basis, you run uncertainly, and without purpose and in vain. As an excellent teacher, the apostle directly puts himself forward as an example. I have someone to strike, namely the devil. …

Commentary on 1 Corinthians ↗

Ambrose of Milan

As a wrestler therefore he enters the lists last of all; he raises his eyes to heaven, he sees that even the heavenly creation was made subject to vanity, not willingly, but by reason of him who hath subjected the same in hope. He sees that the whole creation groaneth in pain together, waiting for redemption. He sees that labour awaits us all. He raises his eyes, he sees the circlets of lights, he surveys the orbs of the moon and stars: For the just, who overcome, shall be as the stars in heaven. …

Letter 49, 5-6 ↗