John Chrysostom

But since boasting might seem to have a place here, see how quickly he checks up, and says, "I can do all things in Christ that strengtheneth me." The success is not mine own, but His who has given me strength.

Homily on Philippians 15 ↗

Theophylact of Ohrid

Since he felt that he had said much about himself, he says: this perfection is not mine, but of Christ who gave me strength.

Commentary on Philippians ↗

Ignatius of Antioch

I give you these instructions, beloved, assured that ye also hold the same opinions [as I do]. But I guard you beforehand from those beasts in the shape of men, whom you must not only not receive, but, if it be possible, not even meet with; only you must pray to God for them, if by any means they may be brought to repentance, which, however, will be very difficult. Yet Jesus Christ, who is our true life, has the power of [effecting] this. …

Epistle of Ignatius to the Smyrnaeans ↗

Thomas Aquinas

Then when he says, I can do all things, he reveals the cause of his constancy saying, I can do all things in him who strengthens me. As if to say: I would not be able to endure want, unless the hand of God supported me: "The hand of the Lord was strong upon me" (Ez. 3:14); "They who wait for the Lord shall renew their strength, they shall mount up with wings like eagles, they shall run and not be weary, they shall walk and not faint" (Is. 40:31).

Commentary on Philippians ↗

Bonaventure

Samson with his hair was the strongest of all: his strength went beyond nature. And why was his strength in seven locks of hair? I say that by the seven locks is signified the sevenfold grace of the Holy Spirit, through whom his strength is made firm. But when he lay in the lap of Delilah and no longer had his hair, he became in strength like other men. Give me one person without grace who could endure what blessed Lawrence endured. For man can do nothing without grace, and nothing is so hard that man cannot endure it with grace. …

Collationes de Septem Donis, Collation 1 ↗