Albert Barnes on 2 John 1:3

Grace be unto you. etc, Rom 1:7. This salutation does not differ from those commonly employed by the sacred writers, except in the emphasis which is placed on the fact that the Lord Jesus Christ is "the Son of the Father." This is much in the style of John, in all of whose writings he dwells much on the fact that the Lord Jesus is the Son of God, and on the importance of reconising that fact in order to the possession of true religion. Comp. 1Jn 2:22,23; 4:15; 5:1,2,10-12, 20.

In truth and love. This phrase is not to be connected with the expression "the Son of the Father." as if it meant that he was ms Son "in truth and love," but is rather to be connected with the "grace, mercy, and peace," referred to, as a prayer that they might be manifested to this family in promoting truth and love.