Letter 7018: Consider what you are undertaking, and you will understand that there is no room for error.

XVIII. FORMULA CONCERNING ARMORERS. [1] Consider what you are undertaking, and you understand that you ought to give no place to faults. For to construct arms well is to wish to preserve the safety of all, since at first sight the enemy himself is terrified by these very arms and begins to yield in spirit, if he recognizes that he does not have the like. And therefore, from that tax-levy onward, invited by the reputation of your character, we have set you over the soldiers and over the makers of arms, so that you may exact from the craftsmen such work as you know can please us. Let confidence in our absence not mislead you. Whatever you do, we see it. Come now, we who by that very practice are able at the very first glance to detect, through the most subtle of inquiries, the errors of craftsmen, and to judge what has been wrought in praiseworthy fashion. [2] See, then, with what diligence, with what zeal that must be made which is to come to our examination. Act, therefore, in such a way that no venality, no fault may sink you, since that which is committed wrongly in such a cause cannot be venial, lest you be punished for the very part in which you have offended. It is a work that produces death and safety: the destruction of those who sin, the protection of the good, against the wicked an ever-necessary aid. This Phoroneus [legendary first king of Argos] is said to have first offered to Juno, so that he might consecrate his invention by the auspice, as they thought, of the deity. These things are necessary in war, comely in peace: these, in short, make weak and frail mortals stronger than all the beasts.

XVIII. FORMULA DE ARMIFACTORIBUS. [1] Considera quid suscipis, et intellegis locum te dare non debere peccatis. arma enim bene construere hoc est salutem velle omnium custodire, quia prima facie ipsis terretur inimicus et incipit animo cedere, si se cognoscit similia non habere. atque ideo ab indictione illa militibus te at fabris armorum, invitati morum tuorum opinione, praefecimus, ut tale opus ab artificibus exigas, quale nobis placere posse cognoscis. securitas te nostrae non inducat absentiae. quicquid feceris nos videmus. age qui usu ipso subtilissima perquisitionis errores artificum possumus prima fronte deprehendere et laudabiliter operata iudicare. [2] Vide ergo qua diligentia, quo studio faciendum est quod ad nostrum venturum constat examen. age itaque ut nulla te venalitas, nulla culpa demergat, quia veniale esse non potest quod in tali causa delinquitur, ne inde puniaris de qua parte peccaveris. opus quod mortem generat et salutem, interitus peccantium, custodia bonorum, contra improbos necessarium semper auxilium. hoc primum Phoroneus Iunoni dicitur obtulisse, ut inventum suum numinis, ut putabant, auspicio consecraret. haec in bello necessaria, in pace decora sunt: haec denique imbecilles fragilesque mortales cunctis beluis efficiunt fortiores.