Praise be to Allaah.
The fasting person is not affected if blood comes out of his
wounds and that does not invalidate his fast. Rather the difference of
scholarly opinion has to do with wet cupping in particular. The more correct
opinion is that it does invalidate the fast because of the text which
indicates that, which is the words of the Prophet (blessings and peace of
Allah be upon him): “The cupper and the one for whom cupping is done both
break their fast.”
Narrated by Abu Dawood, 2367; Ibn Maajah, 1679. Classed as
saheeh by al-Albaani in Saheeh Abi Dawood.
Shaykh Ibn Baaz (may Allah have mercy on him) was asked: If a
person is fasting and he bleeds, does he have to break his fast or should he
complete it?
He replied: Bleeding does not affect him, except in the case
of cupping, if he is treated with cupping. The correct view is that the fast
is broken by cupping. There is a difference of scholarly opinion concerning
the matter, but the correct view is that it does break the fast, because the
Prophet (blessings and peace of Allah be upon him) said: “The cupper and the
one for whom cupping is done both break their fast.” But if he has a
nosebleed or is injured in his foot or hand when he is fasting, his fast
remains valid and that does not affect him.
End quote from the Shaykh’s website on the following link:
http://binbaz.org.sa/mat/18726
Some of the scholars differentiate with regard to bleeding in
general between that which occurs as the result of a person’s actions and
choice and results in a lot of blood coming out, as in the case of donating
blood, for example, which does break the fast, by analogy with cupping, and
that in which he has no choice, such as injuries and the like, which does
not break the fast even if there is a lot of blood. This has been discussed
previously in the answer to question no.
37918.
With regard to pus and the like coming out of wounds, this
does not affect the one who is fasting. It says in ad-Diya’ al-Laami‘ min
al-Khutab al-Jawaami‘ (5/465), by Shaykh Ibn ‘Uthaymeen (may Allah have
mercy on him): The fast is not broken by lancing a wound to drain the pus
from it, even if blood comes out. End quote.
And Allah knows best.