Why does the Bible say we must forgive seventy seven times? Is 7 a holy number?

This question comes from Matthew 18:21-22. Jesus has been talking to the disciples about forgiveness, and so Peter raises a question about personal forgiveness of a brother (believer). Here are the verses in question:

“Then Peter came up and said to him, “Lord, how often will my brother sin against me, and I forgive him? As many as seven times?” Jesus said to him, “I do not say to you seven times, but seventy-seven times.” (Matthew 18:21–22, ESV)

the question Peter asks is not about personal gain through forgiveness or really about the person offended at all. It is a more pastoral approach to trying to forgive so that the relationship between believers may continue.

Peter even goes all out, giving his brother seven times in which he forgives him for an offense. This is how we know Peter is trying to be pastoral and forgiving rather than concerned about himself. The rabbis recommended only three times for forgiveness.

So Peter’s seven times is extreme compared to that standard. Not only this, but the number seven in Hebrew culture and literature is an extremely significant number. It represents the number of perfection. Peter was probably in 10 to say that he would forgive his brother unto perfection.

But Jesus answers unconcerned about the number of times that we forgive one another. It should be an infinite amount of times. Jesus instead tells him he should forgive 77 times. The Greek could be rendered 490 (70×7) but Matthew is referring to Genesis 4:24 in the Septuagint (Greek version of the Old Testament).

There, Cain’s revenge is seven times and Lameh’s revenge will be seventy-seven times. Jesus is basically saying that we should not keep count of the offenses of our brothers and sisters in Christ. He is more concerned that we unanimously and openly forgive them instead of counting the number of offenses.