Faithful means: said and did not deceive, promised and did, loved and did not stop loving. It is someone, who is faithworthy, to whom one can place confidence, on whom one can rely. Such is the God, Who calls us. And thus, we can answer to His call: His faithfulness is the guarantee that He doesn’t call us to harm us. Let's see, where He calls us to. The Greek word "koinonia" means something like brotherly relation, communication of equals. Now, let’s just fancy this picture: there is big and powerful King, who has many subjects. And He has also a Son, Who, naturally, is master over the subjects of His Father. This Son lives of course in a palace, where there is a beautiful garden, in which he spends time. And now the King calls His subjects to come to this palace, to this garden to communicate ON AN EQUAL BASE WITH His Son, thus becoming the sons of the King and coheirs of the Kingdom. We, men got accustomed not to trust, we think that free cheese is only in the mousetrap. We really have to change our habits in order to trust such a King, and the faithfulness of God is a support for us in that.