Musnad Ahmad 280:2

Ibn Numayr narrated to us, al-A‘mash narrated to us, from Mansur, from ‘Amr ibn al-Harith ibn al-Mustaliq, from Zaynab, the wife of ‘Abdullah, who said: The Messenger of Allah, may Allah bless him and grant him peace, commanded us to give charity. He said: "Give charity, O assembly of women." Then she mentioned the rest of the hadith.