"The Great Commission is everyone's responsibility," Dr Michael Oh told thousands of Christians at the end of the Fourth Lausanne Congress on World Evangelization in Incheon, South Korea, on Saturday.

Speaking during the closing ceremony of Lausanne 4, Dr Oh warned against dismissing the Great Commission as "not my business", and said that it must be seen as the Church's "collective responsibility" and "everyone's business".

"The Great Commission is everyone's responsibility. The aggregate result of Christians doing their own thing in their own place - even faithfully - has left us with the trajectory that, year after year, there are more people in the world who have never heard the Gospel than the year before," he said.

In his final keynote address of the congress on Saturday, Dr Oh said that "anything short of a massive realignment of Christian presence and coordination and intentionality" would result in billions of people never hearing the Gospel.

He said he wanted to see more Christians entering different spheres of society to reach people with the Gospel.

"With 3.4 billion people who live among 7,400 unreached people groups in the world and will likely never hear the Good News of Jesus before they die; with 86 per cent of all the world's Muslims, Buddhists and Hindus not knowing a single Christian ... this is not just the responsibility of missionaries and ministers, but of artists, engineers, students, professors, CFOs, CEOs and more," he said.

He continued, "May none of us find comfort in imagining ourselves standing before God one day and giving excuses for our lack of intentionality and collective responsibility by pleading ignorance and saying, sorry, I didn't know."

Collaborative action has been stressed throughout Lausanne 4. On the final day, participants were asked to sign a 'Collaborative Action Commitment' to inspire them to continue seeking ways to work together beyond the congress in sharing the Gospel.

Dr Oh said that no Christian could say they did not need each other. "What impact and greater effectiveness might there be if the ministry of all God's people were to [be] less like the Christian version of 'do random acts of kindness' and more like a coordinated and healthy body of Jesus Christ?" he said.

Also speaking on the final day of the congress was American pastor and bestselling author Rick Warren, who told younger participants below the age of 40, "You have the potential to finish the task and complete the Great Commission."

However, "to make it to the finish line," he said that they needed four things: "mentors, models, partners and friends."

Asking those over the age of 40 to stand up, he told younger participants, "These are the people you should be learning from. You can learn from anybody if you know the right questions. All leaders are learners. These people have already been in ministry for years so they can teach you things that you don't know."

He added, "Now, my prayer for both of these groups is that you will finish well."

Lausanne 4 brought together over 5,000 Christians from over 200 countries to South Korea for a week of collaborating and strategising for world mission.

Discussions were supposed to be underpinned by the Seoul Statement, a 20-page document intended to complement and build upon previous Lausanne theological statements. However, publishing the Seoul Statement prior to the congress proved controversial and created confusion and frustration among many participants who had expected to deliberate over it during the gathering in order to provide feedback before its release.

The strength of feeling led Lausanne leaders to open a feedback mechanism for congress participants to share their reflections on the Seoul Statement's content. 

Lausanne spokesperson Michael du Toit acknowledged the confusion in an email to participants inviting their responses to the Seoul Statement: "We recognise that in introducing the Seoul Statement, we should have been clearer in explaining its purpose and the way in which participants are invited to engage with it."

The feedback will be considered in the coming weeks by the Theology Working Group, who together with Lausanne senior leaders will determine any next steps to be taken. 

The Seoul Statement was not the only controversy at the congress after some participants were upset by comments from guest speaker Ruth Padilla DeBorst criticising Israel and dispensational eschatology.

The comments during her Monday night presentation on justice prompted an apology by congress director David Bennett.

Others were angered by the apology. Valdir Steuernagel, a Brazilian theologian and senior executive adviser to the Lausanne Movement, said it was "problematic" that Lausanne had "distanced itself from one of the most impactful presentations of the event."

Addressing the controversy on Friday, Chris Wright, who serves on Lausanne's board of directors, told reporters that the movement "doesn't claim to be the voice of the whole Christian community", and suggested that members must find a way to live with their differences that does not seek to "pin blame or come up with easy solutions".

"What was said on Monday night was bound to be hurtful for some, and the apology on her behalf hurtful for others. It's very hard to simply say that one side's right or the other side's wrong," he said.

Lausanne 4 was held over seven days at the Songdo Convensia in Incheon, just outside the Korean capital of Seoul. Sessions explored key topics relating to world mission, including leadership, intergenerational discipleship, urban mission, sexuality, faith in the workplace, justice, climate change, and persecution.

The congress coincided with the Lausanne Movement's 50th anniversary, marking half a century since Billy Graham, John Stott and other evangelical leaders came together in Lausanne, Switzerland, in 1974 to found the mission-focused movement.

In his keynote address during the anniversary celebrations on Wednesday, Dr Oh said it was imperative that the Church engage digitally with the world or else "lose the future".

Lausanne 4 was held around the theme of 'Let the Church Declare and Display Christ Together'. It was supported by hundreds of Korean churches and thousands of individual Korean Christians who signed up to pray for the event throughout the week, although a few local Christians protested outside the gathering, claiming that Lausanne was failing to speak out against homosexuality. A Lausanne spokesperson said that the movement had decided not to engage with the protesters.