Blessed Martyrs Designate,— Along with the provision which our lady mother the Church from her bountiful breasts, and each brother out of his private means, makes for your bodily wants in the prison, accept also from me some contribution to your spiritual sustenance; for it is not good that the flesh be feasted and the spirit starve: nay, if that which is weak be carefully looked to, it is but right that that which is still weaker should not be neglected. Not that I am specially entitled to exhort you; yet not only the trainers and overseers, but even the unskilled, nay, all who choose, without the slightest need for it, are wont to animate from afar by their cries the most accomplished gladiators, and from the mere throng of onlookers useful suggestions have sometimes come; first, then, O blessed, grieve not the Holy Spirit, who has entered the prison with you; for if He had not gone with you there, you would not have been there this day.
Do you give all endeavour, therefore, to retain Him; so let Him lead you thence to your Lord. The prison, indeed, is the devil's house as well, wherein he keeps his family. But you have come within its walls for the very purpose of trampling the wicked one under foot in his chosen abode. You had already in pitched battle outside utterly overcome him; let him have no reason, then, to say to himself, “They are now in my domain; with vile hatreds I shall tempt them, with defections or dissensions among themselves.”
Let him fly from your presence, and skulk away into his own abysses, shrunken and torpid, as though he were an outcharmed or smoked-out snake. Give him not the success in his own kingdom of setting you at variance with each other, but let him find you armed and fortified with concord; for peace among you is battle with him. Some, not able to find this peace in the Church, have been used to seek it from the imprisoned martyrs. And so you ought to have it dwelling with you, and to cherish it, and to guard it, that you may be able perhaps to bestow it upon others.
Source: Ad Martyras (New Advent)