Musannaf Ibn Abi Shayba 13:2903

Abu Bakr narrated to us, he said: Muhammad ibn Abd Allah al-Ansari narrated to us, from Ash'ath, from al-Hasan, that he used to say: The testimony of a man for his son is not permissible, nor is the testimony of a son for his father, nor is the testimony of a husband for his wife, nor is the testimony of a wife for her husband.