Is it permissible to spend money allocated for building a mosque on providing potable water to mosques, and what should I do with the remaining money, and would I be sinful for not fulfilling my mother's dying wish to build a mosque after numerous attempts?

Executing a will is obligatory for one-third of the estate, provided it does not violate Islamic law. It is not permissible to alter or delay it, and whoever changes it commits a grave sin. It is obligatory to execute the mother's will to build a mosque, even a small one, if one-third of the estate is sufficient for it, or if someone can make up the deficit. If one-third is not sufficient, the money should be spent on a similar project to what the mother specified, such as contributing to the construction of another mosque, as this is closer to fulfilling her intention. Whatever was previously spent on something other than what was bequeathed must be returned in kind or in value and spent on the mosque.