Allah Ta’ala mentions in Surah Kahf (18:66) in the story of Musa (Alayhi ‘s-Salam) when he was instructed by Allah to go and learn from Khadir (‘alayhi ‘s-Salam)
قَالَ لَهُ مُوسَىٰ هَلْ أَتَّبِعُكَ عَلَىٰ أَن تُعَلِّمَنِ مِمَّا عُلِّمْتَ رُشْدًا
Musa (‘ alayhi ‘s-Salam) said to him (Khidr), “May I be your follower so that you can teach me a part of what you have been taught for (my) guidance?”
In this verse, Musa (‘ alayhi ‘s-Salam) observes a multitude of etiquettes when seeking knowledge from Khadir (‘ alayhi ‘s-Salam), following are twelve ettiquettes specifically mentioned by Imam Razi.