Tafsir of Al-Kahf 18:69

{ولا أعصي لك أمراً} The phrase is in the accusative case (naṣb), functioning as a conjunction to the word {صابراً} (patient). That is: "You will find me patient and not disobedient." Alternatively, it may have no grammatical position, functioning as a new clause coordinated with the main verb {ستجدني} (you will find me).

Musa (peace be upon him), due to his intense desire for knowledge and his eagerness to increase it, hoped that he would be able to remain patient with him after Al-Khidr clarified the reality of the matter. Thus, he promised him patience, while conditioning it upon the will of Allah. He did this because he knew the severity and difficulty of the task, and that the zeal which seizes a reformer upon witnessing corruption is something unbearable.

This was despite his knowledge that the infallible Prophet—whom Allah commanded him to travel to, follow, and acquire knowledge from—was free from committing anything that would cast doubt upon his religion. He knew that whatever appeared outwardly repulsive must have an inward reality that is good and commendable. How much more so, then, is this the case when the underlying reason is not yet known?

{قال فإن اتبعتني فلا تسألني عن شيء حتى أحدث لك منه ذكراً}