Mark Twain, Concerning The Jews, Harper's Magazine, March, 1898
If the statistics are right, the Jews constitute but one per cent. of the human race. It suggests a nebulous dim puff of star-dust lost in the blaze of the Milky Way. Properly the Jew ought hardly to be heard of; but he is heard of, has always been heard of. He is as prominent on the planet as any other people, and his commercial importance is extravagantly out of proportion to the smallness of his bulk. His contributions to the world's list of great names in literature, science, art, music, finance, medicine, and abstruse learning are also away out of proportion to the weakness of his numbers.
He has made a marvellous fight in this world, in all the ages; and has done it with his hands tied behind him. He could be vain of himself, and be excused for it. The Egyptian, the Babylonian, and the Persian rose, filled the planet with sound and splendor, then faded to dream-stuff and passed away; the Greek and the Roman followed, and made a vast noise, and they are gone; other peoples have sprung up and held their torch high for a time, but it burned out, and they sit in twilight now, or have vanished.
The Jew saw them all, beat them all, and is now what he always was, exhibiting no decadence, no infirmities of age, no weakening of his parts, no slowing of his energies, no dulling of his alert and aggressive mind. All things are mortal but the Jew; all other forces pass, but he remains. What is the secret of his immortality?
העמק דבר לנצי״ב
קאי על הפרשה הקודמת דמסיים בשתי מצוות, היינו עיון תורה ודקדוק בה, ובתשובה מאהבת ה׳, ועל זה קאי ״כי המצוה הזאת״.
Ha-Emek Davar, R. Naftali Zvi Yehuda Berlin
It is referring to the previous section, which concludes with two mitzvot, namely deep study of Torah, and repentance out of love of Hashem - and it is about these that the Torah says, "For this mitzvah..."