Where did Malik and al-Awza'i mention matters concerning the mutashabih (ambiguous verses), sometimes discussing it and at other times admonishing against it? And what is the source of this information from ancient books?

It is sufficient for attributing the transmission to Ibn al-Arabi al-Maliki that he was the last of the scholars of al-Andalus. It is possible that he took the statement from his teachers or from a lost book. What Ibn al-Arabi meant by mutashābih (ambiguous) were matters whose outward appearance suggests contradiction, though they are not, such as the contradictory statements of disbelievers, and not the names and attributes of Allah. Imams, such as Imam Malik, believe in the attributes as they literally appear, without distortion, allegorical interpretation (ta'wil), or anthropomorphism (tashbih), as they said, "Pass them on as they came, without kayf (modality/how)," and that asking about the kayfiyyah (modality) is an innovation.