"Somebody asked Hazrat Ali what the difference is between a brother and a friend. He said “a brother is like gold and a friend is like diamond.” So the man asked why are you giving more value to the friend, a diamond is worth more? Imam replied “If gold cracks you can melt it and make it just like it was before. If a diamond cracks, it can never be like it was before."
"Allah did not leave any argument or any excuse for anyone after the event of Ghadir Khum."
— Hazrat Fatemeh Zahra (as), Dala’il al-Imama, p. 38. al-Khisal, vol. 1, p. 173; Bihar al- Anwar, vol 30, p. 124
. (via sange-saboor