Is it permissible to intercede with Allah through the purest heart among us, as in saying: "O Allah, I ask You through the purest heart among us to grant victory to the Muslims"?

There are undoubtedly permissible types of tawassul (seeking intercession): tawassul through the names and attributes of Allah, through righteous deeds, and through the supplication of a living righteous person. Among them are types over which there is disagreement, such as tawassul through the Prophet (peace be upon him) and the righteous. An example of this is the aforementioned supplication ("O Allah, I ask You by the most pious heart") if it refers to the most pious heart among the living. What we prefer and issue a fatwa for is the prohibition of this type of tawassul, even though it is a matter of jurisprudential disagreement in which there is no denial (of the validity of differing opinions).