Musannaf Ibn Abi Shayba 13:2901

Abu Bakr narrated to us, he said: Waki’ narrated to us, he said: Sufyan narrated to us, from Mansur, from Ibrahim, who said: The testimony of a father for his child is not permissible, nor the child for his father, nor the wife for her husband, nor the husband for his wife, nor the slave for his master, nor the master for his slave, nor the partner for his partner, nor [is the testimony of] each one of them for his companion [permissible].