Saint Tikhon of Zadonsk. "On True Christianity". Volume 2.
I am not here talking to you, a Christian, about that faith which consists of the knowledge and keeping of right dogmas: Christians who live lawlessly also have this faith. But I am talking about the faith of the heart, living and saving (about which it was said above), this faith is not in the one who is faulty and does not live according to Christianity, even though he professes and preaches faith. Consider that Christ says: "Ye cannot serve God and mammon" (Mt. 6:24). Just as those who serve God no longer work for mammon, so slaves to mammon no longer serve God. It is impossible to work for God and mammon at the same time, according to the word of Christ. And from this we can conclude that even those who are slaves to any sin no longer serve God. And not serving God, they do not have faith, for without faith it is impossible to serve God. “Without faith it is impossible to please God,” the apostle teaches (Heb. 11:6). To serve and please God is one and the same.