It makes sense that even though we already studied verse 16 when we looked at verses 12-16 as a text, that we look at the second half of the verse again and use it to better understand the meaning of verse 17.  Also, these verses echo much of what John said in 2:5-6, so it is useful to reference the exposition of those verses as we understand these.

16b
The message of verse 16b is that since God is love, the one who abides in love proves that he is most like God and abiding in Him.  John has stated several times in the letter that the believer is the one who abides in God and who has God abiding in him.  To abide in God is to live in ongoing communion with Him and to increasingly become more and more like Him.

John introduced the idea of abiding in God in 2:5-6.  He said the evidence of abiding in God is to walk in the same manner as He (Christ) walked.  In 3:24 he said the evidence of abiding in God is to keep His commandments through the indwelling Spirit.  And He said the commandment of God is to believe in the name of the Son and love one another (3:23).

In the study of 2:6 we described abiding in Him as follows:
What does it mean to abide?  Effectively it means living every day communing with, fellowshipping with, pursuing and knowing our Savior.  Abide carries with it a sense of the present.  We do not abide once in the past – we abide continually.  We spend our lives growing in the knowledge of God and His word.  We live with Him and know Him and His Spirit directs us and teaches us and we begin to see our life and this world as He sees them.  We are not tossed about by circumstances because we are secure in the One who controls them.  Abiding in Christ and Christ abiding in me leads to security, contentment and joy, even in the midst of a fallen world and its attendant trials.

Thus, verse 16b dovetails exactly with what John has said at other points in the letter.  We abide in God when we are like Him and obey Him.  And never are we more like Him and living in obedience to Him than when we abide in love.

So what does it mean to abide in love?  It means I am characterized by love.  My regular and instant response to others is love.  It is what I AM (because God dwells in me and He is love).  Love is the default setting of my life.  When I look at others I love them and I only look at others through the lens of the gospel which I rehearse to myself continually.  I do not just visit love – I LIVE in love.  I do not only love some brothers – I love ALL the brothers.  I do not love sometimes – I love at ALL times.  Love is my home (and home is where I am most comfortable and where I most like to be and the place I naturally return to).  Love is my way of life.  Love forms my opinion of others and dominates my conversation about others.  Love controls my actions and my thoughts.  It means I am like my heavenly Father.

John means that Christians are those who are dwelling in an atmosphere of love, that their lives are controlled by the principles of love, that the great difference ultimately between the Christian and the non-Christian is that love is the controlling factor in the life of the Christian, whereas it is not in that of the non-Christian.  (D Martyn Lloyd-Jones, Life in Christ; 142.)

I know I abide in love when I am patient, kind, not jealous, not a braggart, and not arrogant.  When I do not seek my own.  When I am not provoked and do not take into account a wrong suffered, and do not rejoice in unrighteousness but rejoice with the truth.  When I bear all things, believe all things, hope all things, and endure all things.  When these characteristics define me and are not simply the mark of how I treat certain people at certain times.

That is the standard.  My Father in heaven IS love and since He abides in me and I in Him I will be similarly made out of love.  John has said that I am a child of God (3:1) and that His seed abides in me (3:9).  Thus as His child with His seed I will be a supernatural lover of my fellow children and seed-bearers.  I will ABIDE in love.

17
In verse 17 John states again what he said in verse 12.  God’s love is perfected in us when we love others – when we abide in love through abiding in God.  In 2:5 he said the love of God is perfected in the one who keeps His word.  Keeping His word is evidence that we abide in Him and He in us.  So God’s love is perfected in obedience and the height of obedience is loving one another.  God’s love is perfected in our love for the brethren.

When God’s love is perfected with us we have confidence in the day of judgment.  In 2:28 he said when we abide in Him we will have confidence and not shrink away from Him in shame at His coming.  Since we know that those who abide in Him are characterized by love, it makes sense that those who love will have confidence in the day of judgment.  We will all stand before Him to give an account of our lives.  Those who abide in love in this life will stand assured of their position on that day.  The love they had for others throughout their lives will prove they are His.

That means there is another side to this as well.  Our love for others – or our lack of love for others – has eternal consequences.  If our love assures us we are His, our lack of love assures us we are not.  The one who stands before God and claims to believe His gospel but has no evidence of love in his life will stand condemned.  The one confident in his actions for God but without evidence of love for others will be damned (Matt 7:21-23).  Then He will also say to those on His left, “Depart from me, accursed ones, into the eternal fire which has been prepared for the devil and his angels; for I was hungry, and you gave Me nothing to eat; I was thirsty, and you gave Me nothing to drink; I was a stranger, and you did not invite Me in; naked, and you did not clothe Me; sick, and in prison, and you did not visit Me” (Matt 25:41-43).

If we want to come before Him without fear – if we want to look forward to that day without fear – we must abide in love.  When we see all of life in light of standing before Him we will look at others differently and we will love differently.

John ends verse 17 with the ultimate reason for our confidence on the great day.  Because as He is, so also are we in this world.  The meaning of this could be twofold.  First, we stand before God as He stands – even in this world.  We ARE children of God now and we WILL someday see Jesus in His glorified state and share in His glory (3:2).  Abiding in God with His seed abiding in us we share the privileges of sonship with the Son.  As He was the representation of the Father in this world, so also are we as God’s love is perfected in us.  Standing as Jesus stands gives us great confidence in the day of judgment.

Second, it could mean that we model the Son’s conduct in this world as God’s love is perfected in us.  Our love for others gives us confidence that we do in fact abide in God which in turn gives us confidence in the day of judgment.  This again hearkens back to 2:6 where John said the one who abides in Christ ought himself to walk in the same manner as He walked.  We defined walking as He walked as follows: What does walking in the same manner as He walked look like?  He was meek and lowly.  His only concern was to do the will of the Father and to glorify Him.  He was a man of sorrows – He mourned because of the sin of the world.  He had great compassion for the lost and the needy (read through Matthew’s gospel and the word most used to describe Jesus’ reaction to others is compassion).  He engaged sinners and reached out to them continually.  He did not care at all about material possessions and completely trusted His Father to provide for his physical needs.  He prayed constantly and longed for time with His Father.  Primarily, however, He was characterized by two things – love for the Father that resulted in His desire to glorify Him, and love for others (the very things that make up the greatest commandments – Matt 22:37-40).  These drove Him to the cross.

Jesus’ words in the Sermon on the Mount add to this.  He said we should love our enemies because it would make us like the Father who causes His sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous (Matt 5:45).  He ended this section of the sermon with words that have similar meaning to what John says – Therefore you are to be perfect, as your heavenly Father is perfect (Matt 5:48).  We are to share in the very nature of God – and the nature of God is perfect love based not on the worthiness of men but on Himself.  Thus, when we love with our focus on God we show that we are as He is in this world.

This further amplifies the meaning of God’s love perfected in us.  God loves us and His love is such that it cannot help but come out of us in our love for others.  And when we love others it shows we have the nature of God and in that sense we walk as Jesus walked and are as He is in this world.  The privilege of this statement is staggering.  We will stand with confidence as sons on the day of judgment because as He is, so also are we in this world.

God’s amazing act of love was to send His Son to die for us.  But His death and resurrection are not the end of the story.  God saved us to a life of conformance with the Son (Rom 8:28-30), and conformance with the Son means living a life of love.  The purpose of the gospel is to save us to a life of love – love for God and love for others.

Summary
So our love for others is based in the cross, exposed in the light of judgment, and patterned after Christ.  We approach every human relationship looking back at the cross and forward to the great day.  And we measure ourselves always in light of our likeness to the Son.  Sanctification is not a measure of the sins we no longer commit – it is a measure of how closely we resemble the Son.  And we most closely resemble the Son when we abide in love.

Closing Thought
In his sermon on these verses, D Martyn Lloyd-Jones makes a wonderful statement about dealing with difficult situations in terms of love.  While the comment does not necessarily fit as a conclusion to this text, it is so practical and so good it is worth including.

In practice, having started with great doctrine and especially the doctrine concerning the Son of God, we have to face the situation that confronts us instead of avoiding it and turning our back upon it, excusing ourselves in terms of self-defense.  I must relate every single situation that may develop in my life to the doctrines that I have been enumerating, and especially the doctrine of the cross.  I am referring to that difficult person, that difficult situation in the business or office, or whatever.  I do not care what it is – I repeat, I must take it and put it into the context of the cross.  I must think in terms of that person; I must take the whole situation and just face it in the light of that.  I must say that if God had treated me as I have treated this situation or this person, what would have happened to me?  I must not avoid this; I must bring it into the open.  I must flash the light of Calvary upon it, considering the heart of God which is eternal life.  Is it not the case that half our troubles, and more, are simply due to the fact that we will not face the situation?  We are always avoiding it.  We say, ‘I believe in the doctrine of the cross and God’s love to me, but this situation is extremely difficult.’  But we must bring these things together; the whole of my life must be controlled by this principle – the doctrine of love.  (D Martyn Lloyd-Jones, Life in Christ; 145.)