The trinity is a difficult subject to understand because it is so far beyond our experience of life, but at the same time, it is core to our belief as Christians. I recently wrote a theology of mission for seminary in which I took by best hack at a concise expression of my understanding of this doctrine. The emphasis here is on concise. It means no more and no less than what it says, for more, it would require hundreds of pages to work out all the implications as many books have attempted. My hope is that sharing it here will cause you to take a moment to ponder the nature of the being of God. Questions welcome.
Before we get into the specifics of mission, we must recognize the underlying concepts from which it flows. Key to this entire venture is the doctrine of the Trinity. This doctrine is important as it places at its core the person of God. Two aspects of the trinity that are key to mission are connection/relation and sending/reaching out. What is difficult about understanding the Trinity is its nature of being three distinct beings that are simultaneously one being. This idea is echoed in the phrasing the Bible uses to describe marriage in Genesis 2:24 where it figures the result of the marriage relationship as being that the two individuals “will become one flesh.” Is it referring to a literal organic connection that causes them to be joined as one organism? Of course not. Rather, it is trying to symbolically represent the depth of relationship that two beings experience in the consecrated marriage relationship. If we take this conception and apply it to the Trinity, we can understand it as saying that the three beings are so closely and deeply related as to become one. The most useful semantic conception of this for me is to say that the Trinity is the personification of relationship.
The nature of the person(s) of the Trinity is not the singular important attribute to the discussion of mission. Quite applicable in this discussion is the dynamic of the Trinity as sending/reaching out. The most useful description of this has come through the writing of Killian McDonnell. His description is both clear and concise: “One model of this dynamic is God reaching through the Son in the Spirit to touch and transform the world and to lead them in the Spirit through the Son back to God.” Here we see the Father as continually reaching and receiving, the Son as continually sending and channeling, and the Spirit as continually connecting and directing. This flows directly from the scriptures as Jesus is seen almost as the hand of God in John 5:19. Though God sends the Son, his sending is not complete in the Son, but as the Son sends the Spirit, or more accurately, the Father sends the Spirit in the name of (through) Jesus. The theological peculiarities of this model are not as important as it expressing the core reality that can be seen throughout scripture; namely, God is constantly reaching and sending. If we are to be His people, and are called to strive to display the image of Him that He has placed within us by becoming more and more like Him, we must echo his sending and connecting. This is the spring from which flows the river of mission. It is the divine source for all that we do to bring God’s Kingdom to earth.
 Genesis 2:24 NIV
 This is not personification in the sense of the literary device that gives human qualities to inanimate objects, but in the sense that the trinity expresses relationship by creating a being that ex explained best by relationship. It is personification in the sense that is personifies (embodies, epitomizes, is the incarnation of) relationship.
 Killian McDonnell, The Other Hand of God: The Spirit as Universal Touch and Goal. (Minnesota: Michael Glazier Books, 2003), 3.
 In this verse it says that what the son does, the father also does, in a sense as if Jesus is the physical expression of the reaching of God into the world.
 Acts 1:4,8
 John 14:26