You are reading a tafsir for the group of verses 21:7 to 21:9

فَاسْأَلُوا أَهْلَ الذِّكْرِ‌ إِن كُنتُمْ لَا تَعْلَمُونَ (So, ask the people (having the knowledge) of the message, if you do not know. - 21:7) In this verse, scholars of Injil Evangele) and Torah are referred to as أَهْلَ الذِّكْرِ‌ (people of the message), who had accepted the Holy Prophet's prophethood. Therefore, what it actually means is that if you are not aware whether the prophets of the past were angels or ordinary men then you should find out from the scholars of Injil and Torah as they know perfectly well that all prophets were human beings. It is, therefore, quite possible that here the term اَھلَ :(people of the message) refers to all Jews and Christians (even though they have not believed in the Holy prophethood of the Holy Prophet ﷺ).

Ruling: Qurtubi has said in his exegesis that this verse has made it clear that ignorant persons who are not acquainted with the rules of Shari'ah must seek knowledge from scholars and then follow them accordingly.