Is it permissible to pour oil, over which Qur’an has been recited for healing purposes, and which has become old and unfit for use, into the home garden, given that it is not permissible to pour it into the toilet or the trash?

It is not permissible to pour water over which the Quran has been recited in unclean places like bathrooms, as this goes against the veneration and sanctity of the Quran. However, it is permissible to pour it in a clean, respectable place such as a home garden.