Faith, like active prayer, is a grace. For prayer, when activated by love through the power of the Spirit, renders true faith manifest – the faith that reveals the life of Jesus. If, then, you are aware that such faith is not at work within you, that means your faith is dead and lifeless. In fact you should not even speak of yourself as one of the ‘faithful’ if your faith is merely theoretical and is not actualized by the practice of the commandments or by the Spirit. Thus faith must be evidenced by progress in keeping the commandments, or it must be actualized and translucent in what we do. This is confirmed by St. James when he says, ‘Show me your faith through your works and I will show you the works that I do through my faith (cf. Jas. 2:18). In saying this he makes it clear that grace-inspired faith is evidenced by the keeping of the commandments, just as the commandments are actualized and made translucent by grace-inspired faith. Faith is the root of the commandments or, rather, it is the spring that feeds their growth.
St. Gregory of Sinai
"On Commandments and Doctrines…"