Is the Prophet's (peace be upon him) saying in the story of Moses with Al-Khidr, "May Allah have mercy on Moses; we wished he had been patient so that Allah would tell us more about their story," abrogating his (peace be upon him) saying, "The strong believer is more beloved to Allah than the weak believer," until he said, "for indeed the word 'if' opens the door to the work of Satan"?

The word "if" (لو - law) is used in two ways:

First, as an expression of sorrow and despair over destiny, which is forbidden. This is as in the Almighty's saying: (O you who have believed, do not be like those who disbelieved and said to their brothers when they traveled through the land or went out to fight, "If they had been with us, they would not have died or been killed.") The Prophet, peace and blessings be upon him, also forbade it, saying: "If something befalls you, do not say: 'If only I had done such and such, it would have been such and such.' Rather, say: 'Allah has decreed, and what He willed, He did.' For 'if only' opens the door to the work of Satan."

Second, it can be said to express beneficial knowledge, as in the Almighty's saying: (Had there been within them [i.e., the heavens and earth] gods besides Allah, they both would have been ruined.) Or to express love and desire for good, as in the saying: "If only I had what so-and-so has, I would do what he does." This is permissible. From this category is the Prophet's saying, peace and blessings be upon him: "I wished that Moses had been patient so that Allah might relate to us more of their story."