This is how we know what love is: Jesus Christ laid down his life for us. And we ought to lay down our lives for our brothers and sisters. If anyone has material possessions and sees a brother or sister in need but has no pity on them, how can the love of God be in that person? Dear children, let us not love with words or speech but with actions and in truth.
This is how we know that we belong to the truth and how we set our hearts at rest in his presence: If our hearts condemn us, we know that God is greater than our hearts, and he knows everything. Dear friends, if our hearts do not condemn us, we have confidence before God and receive from him anything we ask, because we keep his commands and do what pleases him. And this is his command: to believe in the name of his Son, Jesus Christ, and to love one another as he commanded us. The one who keeps God’s commands lives in him, and he in them. And this is how we know that he lives in us: We know it by the Spirit he gave us.
1 John 3:16-24 New International Version (NIV)
The Bible is similar to a manual that comes with something we acquire that requires instructions for its use. Sometimes, we don't feel we need the manual until something doesn't work right with the item. It is then we scramble to find that little book that came in the package and try to figure out what may have gone wrong with it's assembly or how we're using it. I love this particular translation of Scripture because it is very clear that we are being instructed on the way to live by the inspired Word of God. "This is how we know . . ." is stated several times in these nine verses.
Jesus came to show us how to live by dying on a cross for our sins. This was love the world had never known. Because of this love and our faith and belief in who He is and all He did to demonstrate His love, we are given the chance to live forever in His Kingdom. It is a reasonable sacrifice to show our appreciation for what we have been freely given by actively loving others. We are instructed to do so in truth by our actions. We can't talk our way to proving our love for someone else to Someone who died to show His love for us. Although some try.
Hearts that condemn are hearts with guilty consciences. We, who believe in Christ as our Savior, enjoy the comfort and help of the Holy Spirit but the Spirit also convicts us. Since God already knows our thoughts and everything we do, the message we receive when our hearts condemn us is the Spirit giving us a head's up about what we may need to correct in our own behavior. The instructions are in the Manual.
We ask for a lot of things in prayer to our gracious and giving God. He asks that we believe in His Son, follow His commands and love one another in truth. We can do this with the help of the Holy Spirit as we follow God's Word. When we accepted Jesus as our Savior and Lord, God came to live in our hearts and we now live in Him. "And this is how we know that he lives in us: We know it by the Spirit he gave us."