Praise be to Allaah.
It is obligatory to offer the prayers on time as enjoined by
Allah, may He be exalted, and it is not permissible to delay them except in
the case of an excuse that make it permissible to put prayers together.
Allah, may He be exalted, says (interpretation of the meaning):
“Verily, the prayer is enjoined on the believers at fixed
hours”
[an-Nisa’ 4:103].
Being careless about the prayer and delaying it until the
time for it is over without any excuse is a major sin, because Allah, may He
be exalted, says (interpretation of the meaning):
“Then, there has succeeded them a posterity who have given
up As-Salat (the prayers) (i.e. made their Salat (prayers) to be lost,
either by not offering them or by not offering them perfectly or by not
offering them in their proper fixed times, etc.) and have followed desires.
So they will be thrown in Hell”
[Maryam 19:59].
Ibn Mas‘ood (may Allah be pleased with him) said concerning
the word ghayy (translated here as “Hell”): This is a valley in Hell which
is very deep and foul.
The Prophet (blessings and peace of Allah be upon him) said:
“Whoever fails to pray ‘Asr, his good deeds will be rendered invalid.”
Narrated by al-Bukhaari, 553.
With regard to putting together Zuhr and ‘Asr, and Maghrib
and ‘Isha’, at the time of the earlier or later prayer, that is permissible
in the case of excuses that have been defined by the scholars, one of which
is so as to alleviate hardship and difficulty. This is appropriate in the
case mentioned here. If the doctor is afraid that if the surgery takes a
long time and when he has finished, the time for ‘Isha’ prayer, for example,
will have ended, then he may put Maghrib and ‘Isha’ together at the time of
the earlier prayer, and offer them at the time of Maghrib. If he is going to
start surgery before the time for Maghrib begins, and he will finish before
the end of the time for ‘Isha’, then he may delay Maghrib and put it
together with ‘Isha’ at the time of the later prayer, after he has finished
doing surgery. The same applies with regard to Zuhr and ‘Asr.
The evidence for that is the report narrated by Muslim (705)
from Ibn ‘Abbaas (may Allah be pleased with him) who said: The Messenger of
Allah (blessings and peace of Allah be upon him) put together Zuhr and ‘Asr,
and Maghrib and ‘Isha’, in Madeenah when there was no fear and no rain.
According to the hadeeth of Wakee‘ he said: I said to Ibn ‘Abbaas: Why did
he do that? He said: So that his ummah would not be subjected to hardship.
Whenever there is difficulty and hardship, it is permissible
to put together Zuhr and ‘Asr, and Maghrib and ‘Isha’. With regard to Fajr,
it cannot be put together with anything else before or after.
Prayer is extremely important, and it is a serious matter. It
is the first thing for which the individual will be brought to account, so
it is essential to pay attention to it and offer prayer regularly and on
time.
We ask Allah to help and guide you.
And Allah knows best.