Musannaf Ibn Abi Shayba 13:2902

Abu Bakr narrated to us, he said: Ibn Abi Za'idah narrated to us, from Ash'ath, from 'Amir, that he used to not permit the testimony of a man for his father, nor the testimony of a woman for her husband. And he used to permit the testimony of a man for his son, and the testimony of a man for his wife.