Musnad Ahmad 1156:53

Waki’ narrated to us, he said: Abdullah bin Sa’id narrated to me, from his father, from Aisha or Umm Salamah—Waki’ said: He (Abdullah bin Sa’id) was in doubt—that the Prophet, may God bless him and grant him peace, said to one of them: "An angel entered upon me in the house who had never entered upon me before. He said to me: 'This son of yours, Al-Husayn, will be killed, and if you wish, I will show you the soil of the earth where he will be killed.'" He said: "Then he brought out some red soil."