Jesus is described as “faithful witness” in Revelation 1:5. In Hebrews 3:1, Jesus is called “Apostle” in Hebrews 3:1. I think these two references inform one another. It seems to me that apostles are those who are faithful witnesses, and faithful witnesses are those who are sent on a mission with a message (apostle).
In addition to a correlation of these terms, there is also a strong “faithful” theme in Hebrews 3. And I have been asking, “what does it mean to be faithful?” One way of answering this is to think about what practices do not constitute biblical faithfulness.
Saying the right things without doing the right things is not faithfulness. Our faith is not primarily made of impressions and appearances, nor is it primarily to consist of testimonies and sermons. Faithful living requires regular obedience.
Merely showing up is not faithfulness – we are to “walk in the Spirit,” not merely watch what others are doing in the Spirit. Faithfulness requires our personal engagement.
Just doing the same things over and over, if they are not the right things, is not faithfulness – Every day brings new challenges which must be met today. Patterns of life must meet the challenges of today, and if they do not, then the patterns need to change.
Staying the same, and refusing to change or grow, is not faithfulness – if God has a plan for your growth, often through trial, then we should not expect that yesterday’s lessons learned will solve today’s tests. You and I must go to God again today to learn how to meet today’s tests.
Neglecting today’s opportunities is not faithfulness – God will give you a once-in-a-lifetime opportunity today. To waste it is not faithfulness.
I'm sure many others will have many more ideas and phrases that will help us to see "what faithfulness isn't."