Faithful as a designation of Christians, means full of faith, trustful, and not simply trustworthy (Acts 10:45; Acts 1:16; 2 Corinthians 6:15; Colossians 1:2; 1 Timothy 4:3, 1 Timothy 1:4; 1 Timothy 1:5; 1 Timothy 1:6; Titus 1:6; Ephesians 1:1; 1 Corinthians 4:17, etc.).
It is used also of God's word or covenant as true and to be trusted (Psalms 119:86, Psalms 1:119; Isaiah 25:1; 1 Timothy 1:15; Revelation 21:5; Revelation 1:22, etc.).