When the Bible speaks about faithfulness it’s talking about a commitment to Someone greater than ourselves. Faithfulness is a lifelong commitment to following the Lord Jesus Christ. The source of our faithfulness to Jesus is the faithfulness of God. However, whereas our faithfulness is inspired by the faithfulness of God, the faithfulness of God is motivated by His delight in His own glory. One way in which God delights in His glory is by having His Spirit make us more like Jesus. To paraphrase John Piper, the more satisfied we are by the faithfulness of God, the more He is glorified in us.