I recently led a Sunday school class at my church on the topic of the trinity. From a biblical perspective, God is revealed as both three distinct persons as well as a singular being. He is in essence three-in-one. This is a difficult concept to understand and perhaps it is not fully comprehensible for human beings. Nevertheless, it is clearly presented in the Bible. Here is a list of Scripture verses that refer to the triunity of God. You may want to examine these passages for yourself.
What's also worth recognizing is that there is a three-in-oneness built into our mortal existence here on earth. Take, for example, a husband and wife. At first it may seem like a marriage consists of only two people who hopefully become one in their marriage over time. In reality, these two individuals are not fully united together until they add God to their partnership. A wedding ceremony is a celebration of two people who intend to join together in harmony. But this is an unlikely outcome without the help and leadership of God.
And even if a husband and wife reach a unity of both thought and action, this does not necessarily mean that their mutually agreed upon objectives are appropriate. Remember that Adam and Eve both agreed to take a bite out of the fruit of the tree of the knowledge of good and evil. They were clearly in harmony on that action, and yet it led to the downfall of the entire world. Consider also, Ananias and Sapphira in the first part of Acts 5. This couple was in total agreement to keep back some of their money and to attempt to deceive the apostles. Look at their terrible result. If these two couples had let God determine their decision-making, and then joined together around God's leadership, they would not have suffered a great loss. The lesson then is clear--partner with God and also with one's spouse. Form a triunity in your marriage.
For those who are not married, this truth remains the same. Any time an individual engages with another person, whether this be with a family member or a friend, he or she can create a triune-like connection. In a sense, they can establish a "practical triunity." They do this by bringing God into their human associations and interactions. But God needs to be the leader, and not just dragged along for the ride. Consider the visual representation of this below:
In this diagram, God is most properly at the top of all of my relationships. I am in a sense, reaching out horizontally to others, as I am simultaneously holding on vertically to God. And the whole connection is rooted in my understanding and appreciation for the sacrificial work of Jesus. This is the practical triunity I should be living out daily.