Musnad Ahmad 1244:6

Yazid ibn Harun narrated to us, he said: Muslim ibn Khalid informed us, from Musa ibn Uqbah, from his mother, from Umm Kulthum. [Abdullah said:] My father said: And Husayn ibn Muhammad narrated it to us, he said: Muslim narrated to us, and he mentioned it, and he said: From his mother, Umm Kulthum bint Abi Salamah, she said: When the Messenger of Allah, peace and blessings of Allah be upon him, married Umm Salamah, he said to her: "I have gifted a garment and some awaqi (ounces) of musk to the Negus, and I do not think but that the Negus has died, and I do not think but that my gift will be returned to me. If it is returned to me, then it is yours." She said: And it was as the Messenger of Allah, peace and blessings of Allah be upon him, said. His gift was returned to him, so he gave each woman of his wives an ounce of musk, and he gave Umm Salamah the remainder of the musk and the garment.