X. Those who swear that they will not receive ordination, declining orders upon oath, must not be driven to perjure themselves, although there does seem to be a canon making concessions to such persons. Yet I have found by experience that perjurers never turn out well. Account must however be taken of the form of the oath, its terms, the frame of mind in which it was taken, and the minutest additions made to the terms, since, if no ground of relief can anywhere be found, such persons must be dismissed. The case, however, of Severus, I mean of the presbyter ordained by him, does seem to me to allow of relief of this kind, if you will permit it. Give directions for the district placed under Mestia, to which the man was appointed, to be reckoned under Vasoda. Thus he will not forswear himself by not departing from the place, and Longinus, having Cyriacus with him, will not leave the Church unprovided for, nor himself be guilty of neglect of work. I moreover shall not be held guilty of taking action in contravention of any canons by making a concession to Cyriacus who had sworn that he would remain at Mindana and yet accepted the transfer. His return will be in accordance with his oath, and his obedience to the arrangement will not be reckoned against him as perjury, because it was not added to his oath that he would not go, even a short time, from Mindana, but would remain there for the future. Severus, who pleads forgetfulness, I shall pardon, only telling him that One who knows what is secret will not overlook the ravaging of His Church by a man of such a character; a man who originally appoints uncanonically, then imposes oaths in violation of the Gospel, then tells a man to perjure himself in the matter of his transfer, and last of all lies in pretended forgetfulness. I am no judge of hearts; I only judge by what I hear; let us leave vengeance to the Lord, and ourselves pardon the common human error of forgetfulness, and receive the man without question.
XI. The man who is guilty of unintentional homicide has given sufficient satisfaction in eleven years. We shall, without doubt, observe what is laid down by Moses in the case of wounded men, and shall not hold a murder to have been committed in the case of a man who lies down after he has been struck, and walks again leaning on his staff. If, however, he does not rise again after he has been struck, nevertheless, from there being no intent to kill, the striker is a homicide, but an unintentional homicide.
XII. The canon absolutely excludes digamists from the ministry.
XIII. Homicide in war is not reckoned by our Fathers as homicide; I presume from their wish to make concession to men fighting on behalf of chastity and true religion. Perhaps, however, it is well to counsel that those whose hands are not clean only abstain from communion for three years.
XIV. A taker of usury, if he consent to spend his unjust gain on the poor, and to be rid for the future of the plague of covetousness, may be received into the ministry.
XV. I am astonished at your requiring exactitude in Scripture, and arguing that there is something forced in the diction of the interpretation which gives the meaning of the original, but does not exactly render what is meant by the Hebrew word. Yet I must not carelessly pass by the question started by an enquiring mind. At the creation of the world, birds of the air and the fishes of the sea had the same origin; for both kinds were produced from the water. The reason is that both have the same characteristics. The latter swim in the water, the former in the air. They are therefore mentioned together. The form of expression is not used without distinction, but of all that lives in the water it is used very properly. The birds of the air and the fishes of the sea are subject to man; and not they alone, but all that passes through the paths of the sea. For every water-creature is not a fish, as for instance the sea monsters, whales, sharks, dolphins, seals, even sea-horses, sea-dogs, saw-fish, sword-fish, and sea-cows; and, if you like, sea nettles, cockles and all hard-shelled creatures of whom none are fish, and all pass through the paths of the sea; so that there are three kinds, birds of the air, fishes of the sea, and all water-creatures which are distinct from fish, and pass through the paths of the sea.
XVI. Naaman was not a great man with the Lord, but with his lord; that is, he was one of the chief princes of the King of the Syrians. Read your Bible carefully, and you will find the answer to your question there.
Source: Letters (New Advent)