2nd and 3rd John are personal letters, written to specific people containing similar ideas to 1st John. There is an emphasis on “walking in the truth”, as well as a reminder of the new commandment of love, which is actually a commandment “we have had from the beginning”.
Paul rejoiced greatly when he heard that the elect lady and her children continued to walk in the truth, and he uses the same language about Gaius. Paul writes, “I have no greater joy than to hear that my children are walking in the truth”, a feeling that reflects Jesus’ own sentiments. “In that same hour he rejoiced in the Holy Spirit and said, I thank you, Father, Lord of heaven and earth, that you have hidden these things from the wise and understanding and revealed them to little children; yes, Father, for such was your gracious will.”
The mystery of the gospel has been revealed to us, and like Paul and Jesus we can rejoice in this, encouraging each other to continue walking in a way that demonstrates the crucial commandment of love.