John Chrysostom : "For thou shall be His witness unto all men of what thou hast seen and heard." "And hear the voice of His mouth." See how high he raises the fact! "For thou shall be His witness - for this, because thou wilt not betray the sight and hearing - both of what thou hast seen, and of what thou hast heard:" by means of both the senses he claims his faithfulness - "to all men." For he did become a witness to Him, and a witness as it ought to be; by what he suffered, by what he did, and by what he said. Such witnesses ought we also to be, and not to betray the things we have been entrusted withal: I speak not only of doctrines, but also of the manner of life. For observe: because he had seen, because he had heard, he bears witness to all men, and nothing hindered him. We too bear witness that there is a Resurrection and numberless good things: we are bound to bear witness of this to all men. "Yes, and we do bear witness," you will say, "and do believe." How; when ye act the contrary? Say now: if any one should call himself a Christian, and then having apostatized should hold with the Jews, would this testimony suffice? By no means: for men would desire the testimony which is borne by the actions. Just so, if we say that there is a Resurrection and numberless good things, and then despise those things and prefer the things here, who will believe us? Not what we say, but what we do, is what all men look to. "Thou shalt be a witness," it says, "unto all men:" not only to the friendly, but also to the unbelievers: for this is what witnesses are for; not to persuade those who know, but those who know not. Let us be trustworthy witnesses. — Homily on Acts 47