Thank you for the interpretative question, “Why does the Bible say we must forgive seventy seven times? Is 7 a holy number?”
There are some Christians and Jews that believe there are significance to the numbers in the Bible. There is some bases for it as God created the earth in 6 days and on the 7th day he rested. The 7th day became the Sabbath rest for the nation of Israel.
In Matthew 18, a question was asked to Jesus about forgiveness and reconciliation. Peter asked how many times must I forgive a brother who sinned against me. The typical response was 3x was more than sufficient for any offense. Peter was even more gracious in saying how about 7 times, would that be sufficient? Jesus’ answer to Peter and to the rest of the disciples was startling. He said 77×7 times or for any practical purposes without limit.
Jesus gives the example of how many times does a person offend God. If God was to count the number of offenses against him each day, each week, each month, and each year, the number would be astronomical. What would we estimate the number of offenses that a person commits against another person or against God? We lose count but God does not forget the offenses against him. If God is willing to forgive us for our repeated sinful attitudes and actions again and again, then it is incumbent that one forgive others if one desires God to forgive us of our offenses against him.
The wonder of I John 1:9 is that God gives his followers a promise that if one confesses one sins against God then he is forgives us. “If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness.” We don’t have to beg God to forgive us. We don’t have to recompense God for our failures. If one is sincere in his/her repentance, God will be more than gracious to forgive us. I am glad that God doesn’t have a limit on forgiveness otherwise we will be in a most pitiful position. Let’s not hold onto our past grudges for God is willing to restore our spiritual wholeness.
SUMMARY: If we are gracious in forgiving others, then God will be gracious in forgiving us.
For more perspectives:
https://www.quora.com/Why-does-the-Bible-say-we-must-forgive-seventy-seven-times-Is-7-a-holy-number