He is suffering from waswaas and fears that his fast may be invalidated because of snuffing water up into the nostrils

Question: 65893

I am (may Allaah heal me) one of those who are affected by waswaas (whispers from the Shaytaan). When doing wudoo’ whilst fasting I try not to exaggerate in snuffing water up into my nostrils, but I feel something in my throat. Is my fasting invalidated by that?.

Praise be to Allah, and peace and blessings be upon the Messenger of Allah and his family.

Firstly:

You have done well by not exaggerating in snuffing up water
into your nostrils, because the Prophet (peace and blessings of Allaah
be upon him) said to Laqeet ibn Sabirah: Do wudoo’ properly, let the water
run between your fingers and toes and exaggerate in snuffing water up into
the nostrils, except when you are fasting.” Narrated by Abu Dawood, 142;
al-Tirmidhi, 788; al-Nasaa’i, 87; Ibn Maajah, 407; classed as saheeh by
al-Albaani in Saheeh al-Tirmidhi.

Secondly:

If a fasting person rinses his mouth or snuffs water up into
his nostrils and some of the water reaches his stomach without any such
intention on his part, then his fast is not broken. Allaah says
(interpretation of the meaning):

“And there is no sin on
you concerning that in which you made a mistake, except in regard to what
your hearts deliberately intend”

[al-Ahzaab 33:5]

This person did not intend in his heart to do the
fast-breaking action, so his fast is still valid.

End quote from al-Sharh al-Mumti’, 6/240, 246.

Thirdly:

The best remedy for waswaas is to ignore it and not to pay
any attention to it, whilst remembering Allaah a great deal, and worshipping
and obeying Him, and avoiding sin.