Actually the reason is simple: Because Jesus wants it. And he prayed for it too.
Every year, the Church celebrates a week of prayer for Christian unity. The week always concludes on January 25, the feast of St. Paul’s conversion.
If you don’t pray for Christian unity, here’s the incredibly simple reason why you should:
John 17:21 gives us this prayer that Jesus prayed at the Last Supper:
I pray not only for them, but also for those who will believe in me through their word, so that they may all be one, as you, Father, are in me and I in you, that they also may be in us, that the world may believe that you sent me.
If Jesus prayed for Christian unity, shouldn’t we?
The Vatican collaborates each year with non-Catholic Christians in creating a theme and resources to pray for Christian unity.
Here is a prayer to pray this week, adapted from those resources. (This year’s theme is from Deuteronomy 16: “Justice and only justice you shall pursue.”)
Prayer of repentance Let us confess before the Lord that we have sinned and ask for forgiveness so that our worship will be pleasing to God. Lord, have mercy. Jesus, your Son, taught us to love one another as a sign of being his disciples. We confess that we have failed to live his commandment of love. Lord, have mercy. Gracious God, You have commissioned us to make our common home a place of justice for all. In your generous love, you send rain on the righteous and the unrighteous and, in Jesus, teach us to love without discrimination. We confess that we have failed to follow this teaching. Lord, have mercy. May almighty God have mercy on us, forgive our sins and lead us to eternal life. Father, may we all be one, as you, Father, are in your Son and your Son is in you. Amen.