Musnad Ahmad 260:1

Al-Qasim ibn Malik al-Muzani Abu Ja'far narrated to us, he said: Jamil ibn Zayd informed me, he said: I accompanied an elder from the Ansar, who mentioned that he had companionship [with the Prophet], he was called Ka'b ibn Zayd or Zayd ibn Ka'b. He narrated to me that the Messenger of Allah, peace and blessings of Allah be upon him, married a woman from Banu Ghifar. When he entered upon her and laid down his garment and sat on the bed, he caught sight of a whiteness on her flank. He moved away from the bed, then said: "Take your garments upon you," and he did not take anything from what he had brought her.