I know that we are not supposed to judge others (see Luke 6:37), and that only God is able to see into the heart of a man (see 1 Samuel 16:7).
But right after command us to not judge, Jesus says:
“No good tree bears bad fruit, nor does a bad tree bear good fruit. Each tree is recognized by its own fruit. People do not pick figs from thornbushes, or grapes from briers. The good man brings good things out of the good stored up in his heart, and the evil man brings evil things out of the evil stored up in his heart. For out of the overflow of his heart his mouth speaks.” Luke 6:43-45 (NIV).
So even though we are not to judge others in terms of pronouncing their ultimate fate — for only Jesus is our ultimate judge — we can still sometimes tell what another has stored up in their heart, whether it be evil or good, by the things that they say.
One who stores up anger, hatred, envy, jealousy, and pride in their heart will often speak ill of others, revealing the evil that they cling to. They will constantly complain about and judge others. Having people such as this in our lives can be truly exhausting as they are difficult to love as the Lord has commanded us to love.
Each of us must be careful of the words we speak and be aware of any evil in our own hearts that words of bitterness might reveal. When we see such bad fruit in the lives of others it is a good time to take an inventory of our own fruitfulness. It is also a good time to practice the lessons our Lord has taught us about how we are to live and not allow such evil to spread to our own hearts.
Above all, I believe the Lord calls us to be a witness to and pray for those in our lives whose bitterness, envy, and pride can cause us such grief. Quoting in part from Proverbs 25:21-22, the apostle Paul wrote:
Do not repay anyone evil for evil. Be careful to do what is right in the eyes of everybody. If it is possible, as far as it depends on you, live at peace with everyone. Do not take revenge, my friends, but leave room for God’s wrath, for it is written: “It is mine to avenge; I will repay,” says the Lord. On the contrary:
“If your enemy is hungry, feed him;
if he is thirsty, give him something to drink.
In doing this, you will heap burning coals on his head.”
Do not be overcome by evil, but overcome evil with good. Romans 12:17-21 (NIV).
When Paul, quoting from Proverbs, says being kind to your enemy “will heap burning coals on his head,” what exactly does he mean? According to Vine’s Complete Expository Dictionary of Old and New Testament Words, this phrase signifies “retribution by kindness, i.e., that, by conferring a favor on your enemy, you recall the wrong he has done to you, so that he repents, with pain of heart.” Vine’s pg. 107. In other words, by repaying another’s evil with kindness, you might cause him to return to the Lord and be saved so that Christ might reign in his heart.
But it is important to remember that it is only by the grace of God that we are able to treat the one whose bad fruit seems to plague our lives with love. It is Christ living in us who loves them and wants to change their heart, to destroy the evil in their heart and replace it with good, who is alone able to give us the capacity to show them love. For it is when we store up Christ in our own hearts that we are able ourselves to bear good fruit.