Aishah reported that the Messenger of Allah ﷺ ordered that a horned ram be brought, one that walked on black, knelt on black, and looked through black. It was brought to him to be sacrificed... the hadith continues.
أن رسول الله ﷺ أمر بكبش أقرن، يطأ في سواد، ويبرك في سواد، وينظر في سواد، فأتي ليضحى به… الحديث.
Muslim narrated it in the chapter on sacrifices (19:1967), from Harun bin Maruf, who said, Abdullah bin Wahb told us, he said, Haywa said, Abu Sakhr told me, from Yazid bin Qusayt, from Urwa bin Zubayr, from Ayesha, and he related it.Khattabi said, her statement, "it treads in blackness," and so on, means that its hooves, the places where it kneels, and what surrounds the area around its eyes and its face are black, while the rest of its body is white.