From The First Apology - Justin Martyr

Reason directs those who are truly pious and philosophical to honor and love only what is true, declining to follow traditional opinions, if these be worthless. For not only does sound reason direct us to refuse the guidance of those who did or taught anything wrong, but it is incumbent on the lover of truth, by all means, and if death be threatened, even before his own life, to choose to do and say what is right. Do you, then, since you are called pious and philosophers, guardians of justice and lovers of learning, give good heed, and hearken to my address; and if you are indeed such, it will be manifested. For we have come, not to flatter you by this writing, nor please you by our address, but to beg that you pass judgment,

And when you hear that we look for a kingdom, you suppose, without making any inquiry, that we speak of a human kingdom; whereas we speak of that which is with God, as appears also from the confession of their faith made by those who are charged with being Christians, though they know that death is the punishment awarded to him who so confesses. For if we looked for a human kingdom, we should also deny our Christ, that we might not be slain; and we should strive to escape detection, that we might obtain what we expect. But since our thoughts are not fixed on the present, we are not concerned when men cut us off; since also death is a debt which must at all events be paid.
Justin Martyr, First Apology 150AD