I found an article that mentions a source for the first quote:
The Woman’s Rights Association had only recently changed its
name to the American Equal Rights Association (AERA)—on
May 10, 1868—and tension within the organization grew quickly
over the Fourteenth Amendment. A few days after the organizational
name change, Susan B. Anthony and Elizabeth Cady Stanton
met with fellow AERA members Wendell Phillips and Theodore
Tilton. During their meeting, Phillips suggested that the organization
turn away from woman suffrage for the moment and focus on
Black suffrage. If anything interfered, he claimed, the chance for
Black enfranchisement might be lost forever. Anthony objected
vehemently. She raised up her right arm and proclaimed: “Look at
this, all of you. And hear me swear that I will cut off this right arm of
mine before I will ever work for or demand the ballot for the negro
and not the woman”
W.E.B. DU BOIS ON
A Critical Analysis of
His Crisis Writings
The article cites this book which was published in 1928.
The second quote is from Anthony's biography (which was written at her request): The Life and Work of Susan B. Anthony by Ida Husted Harper, page 238.
The third quote can be found in History of Woman Suffrage: 1861-1876 edited by Elizabeth Cady Stanton, Susan Brownell Anthony, Matilda Joslyn Gage, Ida Husted Harper, page 383. If I'm reading correctly, the book says that Anthony said it at an event in May 1869 celebrating the anniversary of the American Equal Rights Association.
As the first quote hints at, Anthony was actually fighting for the right for both blacks and women to vote. However, the fact that the 15th Amendment only gave the right for blacks to vote and not women left many, including her, feeling resentment towards blacks:
Throughout much of the 1800s, the women's alcohol temperance movement was a powerful force in the greater push toward women's suffrage. Meanwhile, many suffrage leaders — such as Susan B. Anthony and Elizabeth Cady Stanton — had also championed black equality. Yet in 1870, the suffragists found themselves on opposing ends of the equal-rights battle when Congress passed the 15th Amendment, enabling black men to vote (at least, in theory) — and not women. That measure engendered resentment among some white suffragists, especially in the South.
The Root: How Racism Tainted Women's Suffrage