Is there a contradiction between the Istikhara supplication, especially the part that includes asking Allah to avert the matter if it contains evil, and reliance on Allah (tawakkul) and having a good opinion of Allah, and with the Prophetic hadiths that prohibit making supplications conditional upon Allah's will? And what is the correct interpretation of the Istikhara supplication that removes this ambiguity?

There is no contradiction between the texts of the Istikhara prayer (supplication for guidance) and the principles of reliance on Allah (tawakkul) and having a good opinion of Him (husn al-dhann billah). Indeed, the Istikhara supplication is the essence of reliance, delegation, and having a good opinion of Allah. It does not contradict the prohibition against saying "if You wish" in a decisive supplication, because Istikhara is for matters in which a person is unaware of the best course of action. Thus, one delegates the choice to Allah due to His absolute knowledge.

Therefore, altering the wording of the Istikhara supplication is impermissible, as the Prophet (peace and blessings be upon him) is the one who taught it to us, and he is the exemplary model in reliance on Allah and having a good opinion of Him. Istikhara is a sign of a servant's success, their good opinion of their Lord, and their submission to His judgment.