Whoever says to his brother, You fool! will be liable to the Gehenna of fire. Matt 5:22.

Indeed when charity has been destroyed a person is left to himself and his proprium. He is no longer governed by the Lord by means of internal bonds, which are those of conscience, but by external bonds which are those of the law and those which he imposes upon himself so that he may be powerful and wealthy. And once these bonds are loosed, as indeed happens in the next life, he rushes into the most merciless and disgusting practices, and so to his own condemnation. 'His blood shall be shed who sheds blood' is a law of retaliation very well known to the ancients, by which they judged evil-minded and criminal acts, as is clear from many places in the Word. This law has its origin in the universal law, Do to your neighbour only what you would like others to do to you, Matt 7:12, and also in the fact that the order embracing everything in the next life is such that evil punishes itself, as does falsity also, so that evil and falsity carry their own punishment And because order is such that evil punishes itself, or what amounts to the same, an evil man rushes into a form of punishment answering to his evil, the ancients derived from it their law of retaliation. It also is what is meant by the pronouncement here that 'whoever sheds blood his blood shall be shed', that is, he will rush into condemnation.