3 John 1:3 - Matthew Poole's English Annotations on the Holy Bible

Ver. 3,4. The truth is familiarly used to signify the pure doctrine of Christianity, which in its principal design aims at correspondent practice. That his children, i.e. such as had been converted to Christ by his ministry, \as 1 Corinthians 4:15\ of whom it appears Gaius was one, did walk in the truth; (an apt expression of such correspondent practice); was greatest matter of joy to this holy apostle, especially when the godly lives of such, to whose conversion he had been instrumental, were so observable, as to gain them a testimony from all others that knew them, as it was in the present instance.