The Gospel Message
It was David Berg's lifelong belief that once Christians have a personal knowledge of God, their primary responsibility is to dedicate their time, energy and resources to sharing the Gospel with others. In David's view, there was no other reason for existence. It was this passion for winning others to Christ that had led him to leave organized religion and eventually start the Children of God. He was determined to inculcate the same ardor in his followers. He wrote:
The main thing I care about is getting out the Gospel, getting God's message of love to the lost, to the people who need it, to liberate the captives, save the lost, heal the sick and preach the Gospel to the whole world! 
David understood that it was not enough to simply preach about the love of God. Many people would never be convinced unless they saw a living example of God's love and power in individual Christian's lives. He exhorted his followers to not only preach the Gospel, the Good News of God's love, but to also live it.
"As [the great evangelist D.L.] Moody used to say, 'The only Bible the world reads is the one bound in shoe leather: you and me!' They must see this miracle-working power at work in our own lives, as a genuine living sample and proof that it can happen! This is our major witness." 
In early 1972, the fledgling missionary movement was poised to expand beyond its home bases in North America. David wrote his followers, offering them a great deal of practical advice on how to prepare the missionaries for service overseas. At the close of the letter he outlined what he felt should be the prime motivating force for not only every Christian missionary, but every believer. His entreaty would have an enormous impact on the movement for years to come.
Let me emphasize here the preeminent requisite for any such team ... must be the same driving passion which motivated the Apostle Paul and all the apostles and all the martyrs and every great man or woman of God--in fact, that irresistible compassion which should motivate every Child of God in everything they do, everything you say, everywhere you go, with everybody, and which that great fanatical Apostle summed up in these few famous and ringing words which have cried out from the heart of every true Christian in every true good deed he has ever done, and for which indeed he is willing to die: "the Love of Christ constraineth [compels] us!"