The blood of the martyrs is the seed of the Church

Tertullian: The Apology, translated by Wm. Reeve, (1709 reprinted 1889):

And now, O worshipful judges, go on with your show of justice, and, believe me, you will be juster and juster still in the opinion of the people, the oftener you make them a sacrifice of Christians. Crucify, torture, condemn, grind us all to powder if you can ; your injustice is an illustrious proof of our innocence, and for the proof of this it is that God permits us to suffer; and by your late condemnation of a Christian woman to the lust of a pander, rather than the rage of a lion, you notoriously confess that such a pollution is more abhorred by a Christian than all the torments and deaths you can heap upon her. But do your worst, and rack your inventions for tortures for Christians—it is all to no purpose; you do but attract the world, and make it fall the more in love with our religion; the more you mow us down, the thicker we rise; the Christian blood you spill is like the seed you sow, it springs from the earth again, and fructifies the more.