St. Justin Martyr describes how people before Christ came could be called Christians (of course, also those OT Jews who were faithful to God were faithful to his Son).
Chapter 46. The Word in the world before Christ.
But lest some should, without reason, and for the perversion of what we teach, maintain that we say that Christ was born one hundred and fifty years ago under Cyrenius, and subsequently, in the time of
Pontius Pilate, taught what we say He taught; and should cry out against us as though all
men who were born before Him were irresponsible —let us anticipate and solve the difficulty. We have been taught that
Christ is the
first-born of
God, and we have declared above that He is the Word [Logos} of whom every race of men were partakers; and those who lived according to reason [logos] are
Christians, even though they have been thought
atheists; as, among the Greeks, Socrates and Heraclitus, and men like them; and among the barbarians,
Abraham, and Ananias, and Azarias, and Misael, and Elias, and many others whose actions and names we now decline to recount, because we
know it would be tedious. So that even they who lived before Christ, and lived without reason [logos], were
wicked and hostile to
Christ, and slew those who lived according to reason [logos]. But who, through the power of the Word [Logos], according to the
will of
God the Father and Lord of all, He was born of a
virgin as a
man, and was named Jesus, and was crucified, and died, and rose again, and ascended into heaven, an intelligent man will be able to comprehend from what has been already so largely said. And we, since the
proof of this subject is less needful now, will pass for the present to the
proof of those things which are urgent.
newadvent.org/fathers/0126.htm
