Christian strength comes from God though faith, and is expressed in the unity of love for other Christians. In the Garden of Gethsemane, Jesus prayed for unity among all Christians:
I pray also for those who will believe in me through their message, that all of them may be one, Father, just as you are in me and I am in you. May they also be in us so that the world may believe that you have sent me. I have given them the glory that you gave me, that they may be one as we are one: I in them and you in me. May they be brought to complete unity to let the world know that you sent me and have loved them even as you have loved me.
—John 17:20-23 (NIV-1984).
Love is unity. The three persons of the Trinity have perfect love and perfect unity. Jesus wants also for Christians to have perfect love and perfect unity. However, the Enemy, Satan, does not want this. Satan attacks our faith and our unity.
I am in the process of reading an excellent book by John W. Kleinig entitled, Grace Upon Grace: Spirituality for Today. This book is full of not only excellent theology, but also discusses applications of that theology, in other words: works. (Faith shows itself by what it does. (James 2:18)). One example is a section that discusses the unity of faith. Says Kleinig:
In the front door attack he [Satan] tries to break into the conscience by attacking our faith in Christ; in the back door attack he attempts to gain a secret foothold by attacking our love for our fellow Christians, our brothers and sisters in Christ.
This is how it works! Satan gets another Christian to sin against us in deed or word. It pleases Satan if a person with spiritual significance or authority, such as a parent, pastor, spouse, or leader in the Church sins against us. Their spiritual status, their office, magnifies their offense and intensifies the damage that it does. This is a kind of ritual abuse, the misuse of holy things against us. After the offense has occurred, Satan gets us to brood over it, like a stuck track or a video loop, repeatedly and obsessively in our minds, with ever greater emphasis on the gravity and injustice of it. As we process the offense and its effect on us, Satan gradually distorts our remembrance and our assessment of it. He uses this offense to encourage us to bring our mental accusations against the offender in the court of our minds. There he presides over the proceedings as we hold a secret trial in which we both prosecute and pass judgment on the wrongdoer. The more we brood on the offense, the angrier we get against the offender. We remember all the other offenses that we have suffered from that person and all the other people that have ever hurt us. And that fuels our anger and desire for justice. We maintain that we are in the right; we are justified in our judgment of them. We hold the moral high ground against them. Then before we know it, anger leads to bitterness and resentment. This, in turn, leads to outrage, hatred, and lust for revenge. And so we end up stewing in our own poison. When we begin to hate those whom we should love, Satan has us where he wants us. Once hatred sets in, he can slowly and patiently dislodge us from the Church and from Christ.
—Page 234. Emphasis added.
God says through His apostle (1 John 3:14-15): “We know that we have passed from death to life, because we love our brothers. Anyone who does not love remains in death. Anyone who hates his brother is a murderer, and you know that no murderer has eternal life in him.”
An effective lie always contains much truth. Satan is an effective liar, so he effectively uses the truth of sin among Christians to attack us.
Hatred is spiritual suicide. It marks the end of eternal life, the new life that we have in Christ. Anger is seductive because it makes us feel justified in hating those who have hurt us. We are right, and they are wrong. We are right in hating them and taking revenge on them because they are our enemies. The revenge that we take is subtle and hidden. We don’t usually attack them physically or verbally, but emotionally and spiritually. We write them off and give them the cold shoulder. We reject them in our hearts, dissociate ourselves from them, and treat them as if they were dead for us. That, says John, is spiritual murder. Sadly, by cutting ourselves from our brothers and sisters in Christ, we cut ourselves off from Christ as well. The upshot of that is withdrawal from the family of God and increasing isolation in the darkness of hatred. That is a kind of spiritual suicide, for hatred opens up a secret place for Satan in our hearts.
In Ephesians 4:25-27, Paul urges Christians to learn how to use their anger constructively. If we let the sun go down on our anger and go to sleep angry, we give the devil a “foothold” in our hearts, home, and congregation. Through anger Satan works on us unawares at night, magnifying the offense and distorting our perception of it. We then carry our hurt over to the new day. The longer it lasts, the worse it gets.
This attack from behind is far more common than we realize. It wreaks havoc in the lives of Christians and many Christian communities. It is potent in its impact and destructive in its effects. Yet, God does not stop Satan from using it in the lives of His people. Like the frontal attack, it is a risky tactic because it can so easily backfire on the evil one. In fact, God uses it to destroy our self-righteousness and to build up the Church as a community of grace, a society of forgiven and forgiving sinners. As our anger and desire for justice expose the spiritual fallout from the bad things that others have done to us, we learn, by God’s grace, to face what has happened, seek healing from the damage that has been done, and forgive as we ourselves have been forgiven.
—Pages 235-236. Emphasis added.
The glory that the Father gave the Son is the glory of the cross. Jesus prayed, “I have given them the glory that you gave me, that they may be one as we are one: I in them and you in me. May they be brought to complete unity to let the world know that you sent me and have loved them even as you have loved me.” (John 17:22-23).