"This remorse"

"The ‘irregularity’ [of Nature] also taught man to ‘reverence the happiness of his brethren’. It is on this ‘irregularity’ that Smith grounds what we might call human dignity, that special status that all human beings enjoy simply on account of being alive. This is something that philosophers might otherwise struggle with. That ‘dread’ humans feel of harming others and so being the object of their resentment, which explains our irrational apology for bumping into someone, has wide ramifications:

'As, in the ancient heathen religion, that holy ground which had been consecrated to some god, was not to be trod upon but upon solemn and necessary occasions, and the man who had even ignorantly violated it, became piacular [sinful, blamable] from that moment, and, until proper atonement should be made, incurred the vengeance of that powerful and invisible being to whom it had been set apart; so, by the wisdom of Nature, the happiness of every innocent man is, in the same manner, rendered holy, consecrated, and hedged round against the approach of every other man; not to be wantonly trod upon, not even to be, in any respect, ignorantly and involuntarily violated, without requiring some expiation, some atonement in proportion to the greatness of such undesigned violation' (Adam Smith, The Theory of Moral Sentiments, 107).

Though not in Part vi of The Theory of Moral Sentiments, this passage was one of the important additions Smith made to the sixth edition. Smith had already used earlier editions to depict this remorse in lurid colours, describing it as ‘of all the sentiments which can enter the human breast the most dreadful’. The power of this passion, he wrote, reflected the importance of justice as ‘the main pillar’ upholding society. Compared to it, beneficence is but ‘ornamentation’ (Smith, The Theory of Moral Sentiments, 85–6)."

I know this is a very long quotation but I couldn't find another way out. What is "this remorse" here? (Jonathan Conlin, Critical Lives-Adam Smith)