But the proof. It is literally, ye know the proof of him, unless you prefer to understand it in the imperative mood, know ye; (for there had scarcely been opportunity during that short time to make trial,) but this is not of great moment. What is chiefly to be noticed is, that he furnishes Timothy with an attestation of fidelity and modesty. In evidence of his fidelity, he declares, that he had served with him in the gospel, for such a connection was a token of true sincerity. In evidence of his modesty, he states, that he had submitted to him as to a father. It is not to be wondered, that this virtue is expressly commended by Paul, for it has in all ages been rare. At the present day, where will you find one among the young that will give way to his seniors, even in the smallest thing? to such an extent does impertinence triumph and prevail in the present age! In this passage, as in many others, we see how diligently Paul makes it his aim to put honor upon pious ministers, and that not so much for their own sakes, as on the ground of its being for the advantage of the whole Church, that such persons should be loved and honored, and possess the highest authority.

But ye know the proof of him - You have had evidence among yourselves how faithfully Timothy devoted himself to the promotion of the gospel, and how constantly he served with me. This proves that Timothy was with Paul when he was at Philippi.
As a son with the father - Manifesting the same spirit toward me which a son does toward a father, and evincing the same interest in my work. He did all he could do to aid me, and lighten my labors and sufferings.

Ye know the proof of him, that, as a son with the father, he hath served with me - The Philippians had full proof of the affectionate attachment of Timothy to Paul, for he had labored with him there, as we learn from Acts 16:1-3; Acts 17:14; and we find from what is said here that Timothy was not a servant to the apostle, but that he had served with him. They both labored together in the word and doctrine; for apostles and Christian bishops, in those times, labored as hard as their deacons. There were no sinecures; every one was a laborer, every laborer had his work, and every workman had his wages.

But ye know the proof of him,.... They had had an experiment of him, a trial of his spirit, and a proof of his gifts and ministry, when he was among them with the apostle at his first preaching the Gospel to them, to the conversion of Lydia, and of the jailer, and their households, which laid the foundation of a Gospel church state among them, see Acts 16:3. The Vulgate Latin version reads in the imperative, "know ye the proof of him"; but the former reading is to be preferred:
that as a son with the father, he hath served with me in the Gospel; he served not the apostle, but with him; he served God as the apostle did, in the Gospel of his Son; he served Jesus Christ, whose Gospel he preached, the interest and spread of which he greatly laboured in with him, as a fellow servant or work fellow; see Romans 16:21; which expresses the modesty of the apostle, and the great honour put upon Timothy, and which was not abused by him; for as a son honours, obeys, and imitates his father, so did he honour the apostle, and give him all respect and reverence that was due to him on account of his office, age, and usefulness; and obeyed his orders cheerfully, going wherever he sent him, and doing whatever he bid him; and imitated him in his ministry, in his constancy, diligence, and zeal, having a true filial affection for him.

Rare praise (Nehemiah 7:2).
as a son with the father--Translate, "as a child (serveth) a father."
served with me--When we might expect the sentence to run thus. "As a child serveth a father, so he served me"; he changes it to "served with me" in modesty; as Christians are not servants TO one another," but servants of God WITH one another (compare Philippians 3:17).
in the gospel--Greek, "unto," or "for the Gospel."

As a son with his father - He uses an elegant peculiarity of phrase, speaking partly as of a son, partly as of a fellowlabourer.