What is the ruling on looking at the Mus'haf during recitation without the teacher's knowledge, and is it permissible to obtain an Ijazah in this case, and would this Ijazah be considered valid for granting permission to others?

Obtaining an ijāzah (certification) for memorizing the Quran is a good thing, but what occurred—looking at the mushaf (Quranic text) secretly during the recitation from memory—contradicts the truthfulness commanded by Allah. The Prophet, peace and blessings be upon him, said: "Adhere to truthfulness." And because the ijāzah is a ijāzah for memorization, this ijāzah is not valid due to the absence of complete memorization. Therefore, the surahs that were recited must be re-recited.