Vayikra/Leviticus 19:18
Lo-tikom velo-titor et-beney amecha ve’ahavta lere’acha kamocha ani YHVH.
You shall not take vengeance, nor bear any grudge against the children of your people; but you shall love your neighbor as yourself. I am the LORD.

The talmud gives a definition for bearing a grudge:

And what is bearing a grudge? If one person says to his fellow, "Lend me your ax," and he replies, "No", and on the morrow the second asks, "Lend me your garment," and the first answers: "Here it is. I am not like you who would not lend me"—that is bearing a grudge. (Talmud, Yoma 23a)

Even though the first person lent the garment, he was still holding against his neighbor the fact that he did not lend to him. Bearing a grudge means to remember a person's wrong deed and remind him of it even if we act nicely to him.

Tehillim/Psalms 55:3 Because of the voice of the enemy, Because of the oppression of the wicked. For they bring suffering on me. In anger they hold a grudge against me.

Amos 6:12
Do horses run on the rocky crags? Does one plow there with oxen? But you have turned justice into poison, And the fruit of righteousness into bitterness;

Bitterness towards someone has a negative impact on our righteousness. It is a poison that affects our whole being.

Hebrews 12:15
See to it that no one misses out on YHVH’s grace, that no root of bitterness springing up causes trouble and thus contaminates many,

What we should do instead is to forgive our neighbor.

Mattityahu/Matthew 6:12, 14,16
Forgive us what we have done wrong, as we too have forgiven those who have wronged us. For if you forgive others their offences, your heavenly Father will also forgive you; but if you do not forgive others their offences, your heavenly Father will not forgive yours.

Our ability to forgive others affects how YHVH forgives us.

This truth is also evident in the Talmud as well: "Only if you forgive others will God forgive you." (Babylonian Talmud, Rosh Hashanah 17a)

Mattityahu/Matthew 18:21-22
Then Kefa came up and said to him, "Rabbi, how often can my brother sin against me and I have to forgive him? As many as seven times?" "No, not seven times," answered Yeshua, "but seventy times seven!

There was a tradition that says that you should forgive for a total of three times: "They pardon a man once, that sins against another; and a second time, they pardon him; and a third time, they pardon him. But a fourth time, they do not pardon him. As it is written, "Thus says the Lord, For three transgressions of Israel; yea, for four...". (Amos 2:6) (Yoma 86b)

So Kefa thought he was going beyond the tradition by asking if one should forgive someone sevent times! Yeshua basically answers that if you are keeping track of how many times someone wrongs you, then you are not truly forgiving. How many people are going to keep track of 490 wrongs!

Then Yeshua gives a parable:

Mattityahu/Matthew 18:23-35
Because of this, the Kingdom of Heaven may be compared with a king who decided to settle accounts with his deputies. Right away they brought forward a man who owed him many millions, and since he couldn’t pay, his master ordered that he, his wife, his children and all his possessions be sold to pay the debt. But the servant fell down before him. ‘Be patient with me,’ he begged, ‘and I will pay back everything.' So out of pity for him, the master let him go and forgave the debt. "But as that servant was leaving, he came upon one of his fellow servants who owed him some tiny sum. He grabbed him and began to choke him, crying, ‘Pay back what you owe me!’ His fellow servant fell before him and begged, ‘Be patient with me, and I will pay you back.’ But he refused; instead, he had him thrown in jail until he should repay the debt. When the other servants saw what had happened, they were extremely distressed; and they went and told their master everything that had taken place. Then the master summoned his servant and said, ‘You wicked servant! I forgave you all that debt just because you begged me to do it. Shouldn’t you have had pity on your fellow servant, just as I had pity on you? And in anger his master turned him over to the jailers for punishment until he paid back everything he owed. This is how my heavenly Father will treat you, unless you each forgive your brother from your hearts."

Mark 11:25-26
And when you stand praying, if you have anything against anyone, forgive him; so that your Father in heaven may also forgive your offenses." But if you do not forgive, your Father in heaven will also not forgive your offenses.

Colossians 3:13
Bear with one another; if anyone has a complaint against someone else, forgive him. Indeed, just as the Lord has forgiven you, so you must forgive.

Instead of bearing grudges, we should bear with each other and forgive them.

Ya'akov/James 2:13
For judgment will be without mercy toward one who doesn’t show mercy; but mercy wins out over judgment.

This goes back to the idea of spiritually being the jailor of someone. This is judgement without mercy. But when we show mercy by forgiving each other, then mercy wins over judgement.

Ephesians 4:31-32
Get rid of all bitterness, rage, anger, violent assertiveness and slander, along with all spitefulness. Instead, be kind to each other, tenderhearted; and forgive each other, just as in the Messiah God has also forgiven you.

Shalom v'brakhot v'simcha,
Moreh Chizkiyah Shlomo (Carl)