1 Faustus said: Do I believe the gospel? You ask me if I believe it, though my obedience to its commands shows that I do. I should rather ask you if you believe it, since you give no proof of your belief. I have left my father, mother, wife, and children, and all else that the gospel requires; and do you ask if I believe the gospel? Perhaps you do not know what is called the gospel. The gospel is nothing else than the preaching and the precept of Christ. I have parted with all gold and silver, and have left off carrying money in my purse; content with daily food; without anxiety for tomorrow; and without solicitude about how I shall be fed, or where-withal I shall be clothed: and do you ask if I believe the gospel?
You see in me the blessings of the gospel; and do you ask if I believe the gospel? You see me poor, meek, a peacemaker, pure in heart, mourning, hungering, thirsting, bearing persecutions and enmity for righteousness' sake; and do you doubt my belief in the gospel? One can understand now how John the Baptist, after seeing Jesus, and also hearing of His works, yet asked whether He was Christ. Jesus properly and justly did not deign to reply that He was; but reminded him of the works of which he had already heard: "The blind see, the deaf hear, the dead are raised." In the same way, I might very well reply to your question whether I believe the gospel, by saying, I have left all, father, mother, wife, children, gold, silver, eating, drinking, luxuries, pleasures; take this as a sufficient answer to your questions, and believe that you will be blessed if you are not offended in me.
Source: Reply to Faustus the Manichaean (New Advent)