Second John offers us a brief word of encouragement to continue to walk in God’s light by loving and serving one another. It also warns us to be aware of spiritual counterfeits that distort the truth of the gospel of the incarnate Christ. Thus we are to love, but we are also to show discernment; truth without love leads to harshness and severity, while love without truth produces sloppy sentimentality (cf. “speaking the truth in love”; Ephesians 4:15).
John wrote to encourage his readers not only to hold firm to the apostolic doctrine and practice which “you have heard from the beginning, that you should walk in it” (v. 6), but also to warn them to avoid false teachers and not to take them in or welcome them. They must love one another in the truth and practice discernment so that they do not fall prey to deceptive influences.
From Handbook to Scripture
"Teach us to number our days, that we may gain a heart of wisdom."