I haven't forgotten that I promised to give a fuller treatment to the paragraph Charles Darwin's fans will always refer to while denying that he said what he said in the rest of his second major book dealing with his theory of Natural Selection as explaining evolution, The Descent of Man. I say his fan club and staunch defenders will refer to it because I don't recall ever seeing them give the entire paragraph but, instead, they will cut it and clip it to distort what Darwin said in it. And they never, that I've ever seen, refer to anything else Darwin said immediately before or shortly after this paragraph. As the bulk of that long book, whenever anything impinging on Darwin's belief that the disabled, the economic underclass and members of many families and ethnic groups and even entire races of people, due to their inherent and inherited biological inferiority present a danger to their superiors in the human species. That their survival to reproductive age and ability to have children and propagate their alleged biological inferiority due to the effects of human civilization pose a danger to their superiors and the children of their superiors and, in fact, the entire human species. If you think that's an exaggeration, read the previous paragraph in the post linked to above.
I will give the "aid which we feel impelled to give" paragraph as Darwin published it, then I will point out why it is one of the most hypocritical pieces of double talk in the history of science. Oh, yes, science, this is in a book by one of the most lionized and even deified scientists in the history of science, a book which that scientist presented as science, citing other scientists, supporting their work as reliable, even great science, in some cases in order to bolster what he said. And it was taken as reliable science in the succeeding generations, especially by the eugenicists who Darwin cited in that manner and who, in turn, cited Darwin's eugenic declarations to support their application of Darwinism in involuntarily sterilizing and, in fact, murdering people. Not only eugenics came from natural selection, but the advocacy and practice of killing people deemed to be unfit and whose lives were of lesser worth when and "unfit for life", a concept which was not novel when the Nazis started talking that way.
The aid which we feel impelled to give to the helpless is mainly an incidental result of the instinct of sympathy, which was originally acquired as part of the social instincts, but subsequently rendered, in the manner previously indicated, more tender and more widely diffused. Nor could we check our sympathy, if so urged by hard reason, without deterioration in the noblest part of our nature. The surgeon may harden himself whilst performing an operation, for he knows that he is acting for the good of his patient; but if we were intentionally to neglect the weak and helpless, it could only be for a contingent benefit, with a certain and great present evil. Hence we must bear without complaining the undoubtedly bad effects of the weak surviving and propagating their kind; but there appears to be at least one check in steady action, namely the weaker and inferior members of society not marrying so freely as the sound; and this check might be indefinitely increased, though this is more to be hoped for than expected, by the weak in body or mind refraining from marriage.
I will note that in the previous paragraph, medical care of the "weaker members" of the human species, vaccination, are among the things he lists as perilous means of the "weaker members" not being cut out of he body of humanity. That juxtaposition of medical care in these two paragraphs couldn't have been merely accidental. Again, you don't have to take my word for it, you can read it yourself.