Article avaible in JW.org: https://www.jw.org/en/publications/magazines/watchtower-study-may-2016/questions-from-readers/
How can the congregation express its joy when an announcement is made that someone has been reinstated?
In Luke chapter 15, we find Jesus’ powerful illustration about a man who had a flock of 100 sheep. When one of the sheep was missing, the man left the 99 behind in the wilderness and went after the lost sheep ‘until he found it.’ Jesus continued: “When he has found it, he puts it on his shoulders and rejoices. And when he gets home, he calls his friends and his neighbors together, saying to them, ‘Rejoice with me, for I have found my sheep that was lost.’” In conclusion, Jesus said: “I tell you that in the same way, there will be more joy in heaven over one sinner who repents than over 99 righteous ones who have no need of repentance.”—Luke 15:4-7.
The context shows that Jesus spoke these words in order to correct the thinking of the scribes and the Pharisees, who criticized him for associating with tax collectors and sinners. (Luke 15:1-3) Jesus pointed out that there is joy in heaven when a sinner has come to repentance. We ask, ‘Since there is joy in heaven, should there not also be joy on earth when a sinner has repented, turned around, and made straight paths for his feet?’—Heb. 12:13.