What manner of love
Behold, what manner of love the Father hath bestowed upon us, that we should be called the sons of God: therefore the world knoweth us not, because it knew him not. 1 John 3:1
Consider what is celebrated here: "that we should be called the sons [children] of God." To be a child of God is the pinnacle of all blessing and honor. It carries with it the assurance of God's love, confidence in his care, hope in his faithfulness, and the enjoyment of his fellowship and presence. It fills out the content of the grace of God communicated to us through Jesus Christ. All who are related to God's own Son by faith become by union with him the children of God, and with that all the blessings and privileges which that relation constitutes and implies.
Consider what is known here: this is not something simply to be recognized in the abstract, but for every believer something to behold and enjoy. There is assurance to be had here. Our Heavenly Father is not pleased when we slump around in the shadows of doubt and uncertainty. Rather, we are meant to take him at his word and embrace through Christ this great gift of God's love to us.
Consider what is received here: this love is something which is "bestowed upon us," by grace and grace alone. It is not something we have made ourselves worthy for, but something for which God has made us worthy through his own righteousness. He is the one who gives us the right and authority to become children of God (Jn. 1:12); this is not a right we create, but a right given. And that means that just as our righteousness was not the reason we became children of God, neither will our sins become a reason for our being cast out of his family.
So, brothers and sisters, let us behold this. Let us look at it and wonder and rejoice. We are not waiting for God's love; we have it. We are not waiting to be admitted into his family; we are already in it. Incidentally, in some manuscripts the words, and we are, are added after "that we should be called the sons of God." Not will be, but are right now. And though it is true that the fullness of the glory and inheritance to which our adoption entitles us awaits us, it is sure for us. We are already glorified in the purpose of God (Rom. 8:30) and we can be sure that whatever God purposes will come to pass (Isa. 14:27).