Faithful

as a designation of Christians, means full of faith, trustful,
and not simply trustworthy (Acts 10:45; 16:1; 2 Cor. 6:15; Col.
1:2; 1 Tim. 4:3, 12; 5:16; 6:2; Titus 1:6; Eph. 1:1; 1 Cor.
4:17, etc.).

It is used also of God's word or covenant as true and to be
trusted (Ps. 119:86, 138; Isa. 25:1; 1 Tim. 1:15; Rev. 21:5;
22:6, etc.).