She prayed and forgot to remove her nail polish

Question

Praise be to Allah.

In order to wudoo’ to be valid, it is essential to remove
anything that prevents the water from reaching the skin, such as oil, nail
polish, wax or band-aids. Prayers offered in that state are invalid and
not acceptable.

Al-Nawawi (may Allah have mercy on him) said in al-Majmoo‘
(1/493): If there is wax, dough, henna and the like on one of his limbs,
which prevents water from reaching any part of it, then his tahaarah is not
valid, whether the amount is large or small. If there are traces of henna
and its colour left on the hand, without there being any solid material
left, or elsewhere, or traces of liquid grease whereby water flows over the
limb but does not stay there, his tahaarah is valid. End quote.

It says in Fataawa al-Lajnah al-Daa’imah (5/218):

If the colour is impermeable, then wudoo’ is not valid unless
it is removed before doing wudoo’. If it is not impermeable, then wudoo’ is
valid, as is the case with henna. End quote.

Based on this, if a woman prays and there was anything on her
that prevented water reaching the skin, and she forgot to remove it before
praying, then she is not regarded as sinning because she forgot; but the
prayer is not valid and she has to repeat wudoo’ and the prayer, because of
the report narrated by Muslim (359) from ‘Umar ibn al-Khattaab (may Allah be
pleased with him) who said: A man did wudoo’ and omitted a place the size of
a fingernail on his foot. The Prophet (blessings and peace of Allah upon
him) saw it and said: “Go back and do wudoo’ properly.” So he went back then
he prayed.”

Al-Nawawi (may Allah have mercy on him) said, commenting on
this hadeeth: This hadeeth demonstrates that if a person omits a small spot
of that which must be purified, his purification is not valid, and this is
something on which the scholars are agreed. … This hadeeth also indicates
that if a person omits washing any part of his body and purifying himself
out of ignorance, his purification is not valid. End quote from Saheeh
Muslim.

The Standing Committee was asked:

If I forget, when doing wudoo’, to wash a small part of that
which is washed during wudoo’, then I remember it straight after doing
wudoo’, should I repeat wudoo’ or is it sufficient just to wash that part?

They answered:

Correct sequence is one of the conditions of wudoo’ being
valid. If a person forgets to wash one of the parts of the body that are
washed during wudoo’, or a part thereof, even if it is small, if that
happens during wudoo’ or immediately after, and the traces of the water are
still on his body and have not yet dried, then he should only wash what he
forgot and whatever comes after that.

But if he remembers that he forgot to wash one of the parts
that should be washed in wudoo’, or a part thereof, after his body has
become dry, or he remembers that whilst praying or after he has prayed, then
he should do a new wudoo’ from the beginning, as Allah has prescribed, and
he should repeat the prayer in full, because there was no continuity in this
case and a long time has passed since he finished doing wudoo’. Allah has
enjoined washing all the parts of the body required in wudoo’, so if he
omits any part, even if it is small, of the parts that are to be washed in
wudoo’, it is as if he did not wash it at all. This is indicated in the
report narrated by ‘Umar ibn al-Khattaab (ra): The Messenger of Allah
(blessings and peace of Allah be upon him) saw a man doing wudoo’ and he
omitted a space the size of a fingernail on his foot, so he told him to
repeat the wudoo’ and the prayer; so he did wudoo’ again and then prayed. A
similar report was narrated by Imam Ahmad and Abu Dawood.

And Allah is the source of strength. May Allah sent blessings
and peace upon our Prophet Muhammad and his family and Companions. End
quote.

‘Abd al-‘Azeez ibn ‘Abd-Allah ibn Baaz, ‘Abd al-‘Azeez Aal
al-Shaykh, Bakr Abu Zayd

Fataawa al-Lajnah al-Daa’imah: al-Majmoo‘ah al-Thaaniyyah,
6/92

For more information please see the answer to question no.
103738

And Allah knows best.