Musnad Abu Ya'la al-Mawsili 3:241

Abu Ma'mar Isma'il ibn Ibrahim narrated to us, from Muhammad ibn al-Qasim Abu Ibrahim al-Asadi, from Sa'id ibn 'Ubayd, from 'Ali ibn Rabi'ah, from 'Ali, who said—I do not know it except from the Prophet, may Allah bless him and grant him peace: "If blood surges in any one of you, let him shed it, even if with an arrowhead."