3 John 1:3

For I rejoiced greatly, when brethren came and bare witness unto thy truth, even as thou walkest in truth.

When brethren came ... "The present tense indicates that not on one occasion, but on several, report[11] came." Wilder also agreed that, "The Greek participles here indicate that numerous such reports had come in."[12]

Their witness unto thy truth ... This refers to the enthusiastic reports of traveling missionaries in their appearances in various congregations where they were privileged to speak (3 John 1:1:6). "Witnessing" of this kind was done by the apostles themselves when they reported to "sponsoring" congregations that sent them out.

That thou walkest in truth ... Truth in the apostolic age was almost a technical term meaning "the faith," "the doctrine of Christ," or "the true religion." The modern conception of "all of us disciples are merely trying to find out what truth is" was never heard of by the primitive church. They knew the truth; they had obeyed the truth; they were walking in the truth; they loved the truth. With regard to the great basics of Christianity, one must indeed know them before he can even become a Christian.

[11] Charles C. Ryrie, Wycliffe Bible Commentary, New Testament (Chicago: Moody Press, 1971), p. 1036.

[12] Amos N. Wilder, The Interpreter's Bible, Vol. XII (New York: Abingdon Press, 1956), p. 309.