The passage
      v7-8. John exhorts us to love one another, for love is of the being of God. That is, love is an aspect of the Divine nature which we can share. Those who love have entered into a relationship with God - they know him, believe in him, are born of him, are one with him. Those who do not love, do not know God. The reason for this is simple enough, since God's very nature is expressed in love, then love will rub off on those who are in a relationship with him, but will be lacking in those who are distant from him.
      v9-10. John goes on to clarify the idea of "love" by giving us to two examples of love in operation. First, God's love is demonstrated in the sending of Jesus to die for us. Here lies the perfect expression of love. Such love is self-giving to the point of self-sacrifice. The depth of this love is evident in the sending of the Son by the Father. Jesus was unique and yet the Father sent him into a hostile environment where he would inevitably be affronted. Such is God's love for us. More than this, Jesus was sent as an atoning sacrifice for our sins. This is a very important theological statement detailing for us the meaning of the cross.
      v11-12. Second, God's love is seen in the love of the brotherhood; it is evidenced in the love that exists between believers. In fact, John makes a statement which is quite amazing. The very essence of God, which can't be seen, can be experienced in the loving relationships that exist between believers. We can touch Jesus in the loving touch of a brother. Of course, the world can also see God in this love. "All men will know that you are my disciples if you love one another", Jn.13:35. It is "the ultimate apologetic" said Francis Schaeffer. As to its practical expression, no better illustration exists than when Jesus washed his disciples feet, Jn.13:14-17. Of course, the "how" to love is always going to remain our problem. John simply rests on the idea, "since God so loved us", that is, the death of Christ supplies our motivation. Christ's death freed us from both the curse and the dominion of sin. On the one hand, we are no longer condemned, but totally accepted in God's sight. On the other hand, through the indwelling Spirit, the very essence of Divine love resides within us, motivating us to love as Christ loved. Our responsibility is but to cooperate with the Spirit's renewing work.

Know where you stand
      "I write this to you that you will not sin." 2:1.
      Central to John's purpose in this letter, is his desire to have us examine our lives to see whether we stand with Christ, or against Christ. He is primarily concerned with those who are frauds, rebels, sinners, lost, but who don't know it. So, this letter is not all about assurance. In fact, the more we read the more we are disturbed, and that's a good thing. John doesn't want us to live a lie.
      At this particular moment in our lives we may feel that we are active faithful Christians, but at the same time we may well be fooling ourselves. For this reason, John comes up with a number of tests. In our passage for study, John writes of the test of love.
      Love is an active caring compassion focused by revealed truth. It is the subject of the passage we have just studied. We will never love perfectly, for it is an ideal, so the best we can do is push toward it. If we find ourselves tending toward hate, if we find in our lives little care toward the needs of our brothers and sisters, then such is an evidence that we may well be standing outside the grace of God. Repentance will confirm our standing, but continued hate will only evidence our coming doom. By the way, John uses "hate" in terms that are far stronger than just being angry with a brother who has trodden on our toes. There will always be times when we will get angry with a brother.
      A child of God is recognized by the fruit they bear. Know therefore and observe, the day of testing will come for each one of us, and when it comes, know that if we enter into rebellion we are living in the dark. To continue in the dark is to confirm that we are of the dark and not of the light.
      Each one of us faces a whole range of social, intellectual and hormonal crises in life. They serve as times of testing. Few come through these times unscathed. We may waver, slip and fall. No one can claim to come through life unbloodied, but if Jesus is our friend, we will stand loyal to him. In the long run, we will turn from the darkness, and on those occasions when we fall, we will pick ourselves up out of the dust and kneel before our merciful God.
      So, rough times will come, and if we find our love growing cold then its time to move back to the foot of the cross.

v7
      agapwmen (agapaw) pres. subj. "love [one another]" - let us love. Hortatory subjunctive.
      hJ agaph ek tou qeou estin "love comes from God" - love of God is. "This love is from God", Lenski, suggesting that the article makes the "love" demonstrative, although abstract nouns often have an article. John is unlikely to be suggesting that all forms of love come from God, given that God is the origin of all things (true though this is), but rather that the special love of the brotherhood, exampled in the sacrificial love of Christ, originates from God, is divine.
      gegennhtai (gennaw) perf. pas. "has been born" - Given the context, born of God has a similar meaning to knowing God. John says that a person who loves, knows God. This again indicates that love is certainly not some fuzzy emotion, but rather active compassion / mercy. The child of God will exhibit this characteristic of the Father (albeit imperfectly) because they "know" God, are "born of" God.

v8
      oJti "because" - Expressing cause/reason.
      oJ qeoV agaph estin "God is love" - "Is love" is the predicate of the clause, with "God" as the subject, the predicate serving to express a truth about God. Thus, the alternate is not true, ie. "love is God." When John describes God as love, he is not just describing his character, but rather the essence of his being. He is a caring relational God. The very nature of his being is triune - one God in three persons - and this provides the shape for his love. God interrelates within himself. The capacity for human beings to love is part of the image of God within us. Yet, John's point is not so much to note this common grace possessed by all humans, but rather to pinpoint a special grace for God's children, namely, brotherly love. For John, such love is the evidence that we are a child of God. Of course, we must not assume that "love" is an all encompassing definition for God's Character. Other one-liners are just as important: "God is spirit", "God is truth", ...

v9
      en toutw/ "this" - by this. Instrumental; "by this means was the love manifested to us, namely, that he sent his only son into the world."
      tou qeou "God" - [the love] of God. Subjective genitive, ie. God produces the action, he does the loving.
      afanerwqh (fanerow) aor. pas. "showed" - was manifested, revealed, made clear... God is the agent of the manifesting and the agent of "love", prompting the NIV to ignore the passive. For the passive sense, "This is how the love of God has appeared for us", Moffatt.
      en hJmin "among us" - in us. Locative. "Toward us", AV, makes sense, but not true to the grammar. "Among us", NIV, RSV, doesn't make sense. "To us", NEB, makes sense. Possibly God's love "in us", "indwelling us", "within us".
      oJti "-" - that. Introducing a noun clause, appositional, or epexegetic of "by this means", see above, "by this means .... namely that ...."
      monogenh adj. "only [son]" - only begotten, one and only, one of a kind, unique. "Unique", in the sense of the only one of its kind, gives the best sense of the word here, rather than the sense of "only son."
      iJna + subj. "that" - that. Introducing a purpose clause, "in order that."
      zhswmen (zaw) aor. subj. "we might live" - we may live. John touches on the reason for the sending of the Son, namely, life eternal for believers.

v10
      en toutw/ "this" - Instrumental, as above, and referring to the noun clause introduced by oJti, "by this means is love demonstrated .... namely, that God loved us and sent ..."
      hgaphkamen (agapaw) perf. "[we] loved [God]" - have loved. Perfect tense implies a past act with ongoing action. God has loved us and continues to love us.
      alla "but" - Contrastive. Love is evidenced, not in our love of God, but of his love of us.
      hgaphsen (agapaw) aor. "[he] loved [us]" love. Aorist tense expresses a completed act. God's ongoing love expressed in a single moment of time, "his love for us - in the sending of his son", Moffatt.
      iJlasmon (oV) "atoning sacrifice" - a propitiation, an expiation. Accusative object complement of the accusative "Son", functioning as a predicate of "Son", ie. saying something about "son"; the "Son" serves as a "propitiation / expiation", probably in the sense that he is the means by which propitiation is achieved. We need to note that the NIV, as with many newer translations, fails to maintain the accuracy of the text when it replaces "propitiation" with "atonement". Propitiation means that the sacrificial offering of the person of Jesus achieved the turning aside of the righteous wrath of God. Jesus suffered in our stead taking the penalty for our sins. Such is the greatness of God's love for us. This indeed is love.
      peri + gen. "for" - concerning, about. Best taken as referring to, "serving as a propitiation / expiation with reference to our sins"; "that he might be the means of expiating our sins", Cassirer.

v11
      ei + ind. "since" - if. Introducing a 1st. class condition, where the condition is assumed to be true, so "since it is a fact that."
      ofeilomen (ofeilw) "we [also] ought" - we owe, we ought, be morally obligated. Expressing obligation, duty.
      agapan (agapaw) pres. inf. "to love" - The infinitive is complementary, complementing the sense of the verb "ought." "If God loved us like that, it is our bounded duty to love each other", Barclay.