'Whoever causes one of these little ones who believe [in me] to sin, it would be better for him if a great millstone were put around his neck and he were thrown into the sea..." — Mk 9:42

Several years back, I was asked by my cousin if I could co-officiate at her wedding, which was going to be celebrated in the Armenian Apostolic Church. She was worried that a Catholic priest could not participate in a wedding in the church of another Christian denomination. When I told her I would be able to participate, and the marriage would be recognized by the Catholic Church, she was delighted.

That situation is not unusual. People so often do not understand ecumenism, the relationship between all the Christian denominations, Catholic, Orthodox, Protestant and Evangelical churches. We all work together to further the mission of Jesus Christ.

That's not always the way it was. You might remember a time when a Catholic or Protestant was not allowed to be in the wedding of someone of a different faith. If a Catholic married a Protestant, the wedding either took place in the rectory or outside the sanctuary of the church. There was a time when a Catholic could not even be a guest at a non-Catholic wedding.

These are real-life examples of the statement the Apostle John presents to Jesus in Sunday’s Gospel (Mk 9:38-43,45,47-48): “'Teacher, we saw someone driving out demons in your name, and we tried to prevent him because he does not follow us.' Jesus responded by saying, 'Do not prevent him.'”

Jesus makes it clear that the work of God can’t be accomplished by someone who does not believe. The challenge Jesus gives to the believer is that we can’t shut out others because they may be different from us in the way they worship, or in what they believe or how they live, for they, too, may be called by God to serve. Moses says as much in the first reading (Num 11:25-29), when two men receive the gift of prophesy: “Would that the Lord might bestow His spirit on them all.”

It is this understanding that guides Church teaching on ecumenism. Vatican II, in the 1960s, brought a new spirit of cooperation among the various denominations of Christianity with the Decree on Ecumenism, “Unitatis Redintegratio."

The decree speaks about the restoration of unity among Christians: “Christ the Lord founded one Church and one Church only. However, many Christian communions present themselves to men as the true inheritors of Jesus Christ; all indeed profess to be followers of the Lord, but differ in mind and go their different ways, as if Christ Himself were divided. Certainly, such division openly contradicts the will of Christ, scandalizes the world and damages that most holy cause, the preaching of the Gospel to every creature.”

We Christians have been the greatest obstacle to the Gospel being preached, because we have allowed differences to overshadow what we all share in common: Jesus Christ.

God gives us His law, as we hear in Psalm 19 (8,10,12-13,14): “The precepts of the Lord give joy to the heart.” God’s law is fair and just, never excluding people but inviting them into a relationship with God. The law of God is not restrictive, but God’s covenant brings us lasting freedom.

The second reading (Jas 5:1-6) speaks about the materially wealthy and how their self-absorption will lead to their decay. When we are self-absorbed, we shut out others from our lives, from sharing the wealth of the Gospel message. Because Christian denominations have been divided over centuries, our divisions have shut others out from hearing the Gospel proclaimed.

We are called to witness to our love of Christ to one another, especially among Christians. We have missed many opportunities to establish the kingdom of God here and now. Maybe we need the same kind of cooperation among Christian Churches as we have with the sacrament of marriage. That cooperation among people of faith can occur in all areas of Christian living. We can help create that cooperation by joining ecumenical associations to help build cooperation and understanding among all Christian people.

Jesus asks us to cooperate with one another by letting go of anything that does not reflect the presence of Jesus. If Jesus is for us, how can we allow anything in our lives that is against Jesus, and thus against one another, as well?