Assalaamu alaykum wa rahmatullaahi wa barakaatuhu. Is it permissible to apply oil, medication, or water and so on under one's feet, on which one blows after doing Ruqyah (healing through Quranic recitation and supplication)? Also, please advice regarding the application of ones saliva under their feet after recitating Surah Al Faatihah. I am asking as it is under the feet, and I do not know if that is correct or not given that Quran recitation is done in both matters. May Allaah reward you, Shaykh.

All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger. 

There is nothing wrong if this is done with the intention of Ruqyah provided that the feet are pure. If the feet are impure, however, then one should avoid this until they become pure, as this is a form of despising the Words of Allah.

Indeed, the scholars stated that the Words of Allah must be protected from being mixed with impurities, as Allah says (what means): {That [is so]. And whoever honors the symbols of Allah - indeed, it is from the piety of hearts...} [Quran 22:32] Allah also says (what means): {That [has been commanded], and whoever honors the sacred ordinances of Allah - it is best for him in the sight of his Lord.} [Quran 22:30]

It was narrated from Imaam Ahmad that it is disliked to perform Ghusl (ritual shower) with water upon which Ruqyah was recited in order to safeguard it from impure drains. Ibn Muflih, from the Hanbali School of jurisprudence, said in Al-Aadaab Ash-Shar’iyyah, “Al-Khallaal said that it is disliked to perform Ghusl with it, because in general the water with which a person performs Ghusl runs down drains and toilets, so it is an obligation that the water of the Quran be preserved from this.”

Besides, Fath Al-’Ali Al-Malik fil-Fatwa ‘ala Mathhab Al-Imaam Maalik authored by ‘Ulaysh reads:

“Question: What is your opinion regarding washing the board on which the Quran was written in a place that is impure or where people walk with their shoes, and he answered, ‘Praise be to Allah, and blessing and peace be upon Prophet Muhammad, the Messenger of Allah; this is not permissible. At-Tirmithi al-Hakeem said, ‘Among the sacredness of the Quran is that it should not be wiped off the board by spitting on it; rather, it should be washed with water. Part of its sacredness is that if it is washed with water, then this water should not be poured into an impure place or a place where people walk; that water that was used to wash the written Quran has its sacredness, and the Salaf (righteous predecessors) used to seek treatment with it.’’ This was quoted by Al-Qurtubi in the introduction of his Tafseer. According to Al-Madkhal, this water that is used to wash the board on which the Quran was written should either be poured in the sea, or in a well, or in a pure hole on which people do not walk; and Allah knows best, and peace and blessings be upon our Prophet Muhammad .”

Allah knows best.