And this is his commandment, that we believe in the name of his Son Jesus Christ and love one another, just as he has commanded us. – 1 John 3:23 ESV
Two simple things: Believe in Jesus and love one another. But oh, how difficult those two things can be to do. The first one seems so easy. In fact, all of us who have placed our faith in Christ as our Savior have already done it. We have already believed in Jesus. But there is a sense in which we must continue to believe in Jesus. The word “believe” that John uses is in the aorist tense. Typically, we end up translating aorist verbs as past tense, but in the Greek the concept of an aorist verb is considered without regard for past, present, or future time. We don't have an equivalent tense in English. So in reality, our belief in Jesus is to be past, present and future. It is non-ending. One of the reasons John put so much emphasis on abiding in Christ is that it is the key to our fruitfulness and without abiding we can do nothing. “Abide in me, and I in you. As the branch cannot bear fruit by itself, unless it abides in the vine, neither can you, unless you abide in me. I am the vine; you are the branches. Whoever abides in me and I in him, he it is that bears much fruit, for apart from me you can do nothing” (John 15:4-5 ESV). To abide in Him is to believe in Him. We must continue to rely upon Him for our sanctification just as we did for our salvation. Without Christ, we cannot be fruitful. Without Christ, we cannot grow in Christ-likeness. Without Christ, we cannot love others. Without Christ, we cannot do anything.
Which brings us to the second simple statement we find so hard to do: Love one another. It would seem that our struggle with loving one another is directly linked to our unwillingness to believe in Christ. Yes, we believed in Him for our salvation, but we sometimes fail to believe in Him for all that follows after that. When Jesus said that He would send us the Holy Spirit, we must believe that what He said was true. We must believe the promise of Jesus even when we don't feel the Holy Spirit's presence in our lives. We must also believe that the Holy Spirit is our helper, comforter and guide just as Jesus said He would be. We must believe that He, the Spirit, is the Spirit of truth just as Jesus said He would be. We must believe that the Holy Spirit will teach us “about everything, and is true, and is no lie” (1 John 2:27 ESV). Our capacity to love one another is not some self-manufactured, man-made kind of love we conjure up out of our own will power. It is a fruit of abiding in Christ and relying upon the Spirit of God. Believing and loving go hand in hand. We love because He first loved us. Without Christ, we will find it impossible to love others. In the very next chapter, John tells us, “Beloved, let us love one another, for love is from God, and whoever loves has been born of God, and knows God” (1 John 4:7 ESV). Our capacity to love comes from the love of God for us. But we must believe that. We must rely upon that. We must understand that all of our righteous deeds, apart from Christ, are like filthy rags. Even on our best day, our best efforts don't measure up. We are completely dependent upon Christ for all that we need to walk as He walked (1 John 1:6) and love like He loved ( John 15:12).
To believe in the name of His Son Jesus Christ is to believe that Jesus is who God claimed Him to be. He is the Son of God. He is the Messiah, the Savior of the world. He is the sinless Lamb of God who died on the cross in order to satisfy the just demands of a righteous God. He is the risen Lord of lords. He is our advocate, our mediator, who sits at the right hand of God interceding on our behalf. He is our source of strength, hope, salvation, mercy, grace, and love each and every day of our lives. He is the vine and we are the branches. Without Him we can do nothing. We can't live without Him. We can't love without Him. But we must believe that. We must abide in that. We must remain totally dependent upon Him for all that we need, from our salvation all the way to our ultimate glorification, and everything in between.