Barnes New Testament Notes

Verse 4. I have no greater joy than to hear that my children walk in truth. That they adhere steadfastly to the truth, and that they live in accordance with it. This is such language as would be used by an aged apostle when speaking of those who had been converted by his instrumentality, and who looked up to him as a father; and we may, therefore, infer that Gaius had been converted under the ministry of John, and that he was probably a much younger man than he was. John, the aged apostle, says that he had no higher happiness than to learn, respecting those who regarded him as their spiritual father, that they were steadfast in their adherence to the doctrines of religion. The same thing may be said now

(a.) of all the ministers of the gospel, that their highest comfort is found in the fact that those to whom they minister, whether still under their care or removed from them, persevere in a steadfast attachment to the true doctrines of religion, and live accordingly; and

(b.) of all Christian parents respecting their own children. The highest joy that a Christian parent can have is to know that his children, whether at home or abroad, adhere to the truths of religion, and live in accordance with the requirements of the gospel of Christ. If a child wished to confer the highest possible happiness on his parents when with them, it would be by becoming a decided Christian; if, when abroad, in foreign lands or his own, he wished to convey intelligence to them that would most thrill their hearts with joy, it would be to announce to them that he had given his heart to God. There is no joy in a family like that when children are converted; there is no news that comes from abroad that diffuses so much happiness through the domestic circle as the intelligence that a child is truly converted to the Saylout. There is nothing that would give more peace to the dying pillow of the Christian parent, than to be able to leave the world with the assurance that his children would always walk in truth.

{b} "joy" Pr 23:24