Is work one of the excuses for which it is permissible to delay prayer beyond its time?

It is not permissible
for a Muslim to delay his prayers beyond the time when they are due without
a legitimate excuse. Legitimate excuses which allow a Muslim to delay his
prayers until the time for them is over include sleeping and forgetting.
Doing worldly work is not an excuse for not praying or for delaying a prayer
until its time is over. Rather one of the characteristics of the sincere
believers is that they do not let business or trade distract them from
remembering Allaah and establishing regular prayer. 

Allaah says
(interpretation of the meaning): 

“In houses (mosques) which Allaah
has ordered to be raised (to be cleaned, and to be honoured), in them His
Name is remembered [i.e. Adhaan, Iqaamah, Salaah (prayers), invocations,
recitation of the Qur’aan]. Therein glorify Him (Allaah) in the mornings and
in the afternoons or the evenings,

37. Men whom neither
trade nor sale (business) diverts from the remembrance of Allaah (with heart
and tongue) nor from performing As-Salaah (Iqaamat-as-Salaah) nor from
giving the Zakaah. They fear a Day when hearts and eyes will be overturned
(out of the horror of the torment of the Day of Resurrection).

38. That Allaah may
reward them according to the best of their deeds, and add even more for them
out of His Grace. And Allaah provides without measure to whom He wills”

[al-Noor 24:36-38] 

Even though these men
engaged in trade, buying and selling, that was no excuse and it did not
distract them from giving precedence to “the remembrance of Allaah (with
heart and tongue) nor from performing As-Salaah (Iqaamat-as-Salaah) nor from
giving the Zakaah.”  Rather they made obedience to Allaah and worship of
Him their ultimate goal and purpose, and whatever came between them and that
goal, they rejected it. 

Because giving up
worldly interests is hard for most people, and earning and various kinds of
trade are dear to them, and it is hard for them to give that up in most
cases, and to give precedence to the rights of Allaah, Allaah mentions that
which will motivate and encourage them, as He says: “They fear a Day when
hearts and eyes will be overturned (out of the horror of the torment of the
Day of Resurrection)” – because of the intensity of its horrors and
suffering. Hence they will fear that Day, so it become easier for them to
strive for the Hereafter and give up that which distracts them from it. 

Tafseer al-Sa’di. 

Concerning the obligation of
offering prayers and the ruling on its timing, Allaah says (interpretation
of the meaning): 

“Verily, As-Salaah
(the prayer) is enjoined on the believers at fixed hours”

[al-Nisa’ 4:103]. 

Shaykh ‘Abd al-Rahmaan
al-Sa’di said: 

This means it is
enjoined at its time, which indicates that it is obligatory and that it has
a time (to be offered) and is not valid at any other time. These are the
times that are well known among the Muslims, young and old, scholars and
ignorant. They learned that from their Prophet Muhammad (peace and
blessings of Allaah be upon him) who said: “Pray as you have seen me
praying.” The phrase “on the believers”
indicates that prayer is the measure of faith, and a the quality of person’s
prayers corresponds with his level of faith. 

Tafseer al-Sa’di. 

And Allaah says,
warning those who delay their prayers until the time for them is over with
no legitimate excuse (interpretation of the meaning): 

“Then, there has succeeded them a
posterity who have given up As-Salaat (the prayers) [i.e. made their Salaat
(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] and have
followed lusts. So they will be thrown in Hell.

60. Except those who
repent and believe (in the Oneness of Allaah and His Messenger Muhammad),
and work righteousness. Such will enter Paradise and they will not be
wronged in aught”

[Maryam 19:59-60] 

And Allaah says
(interpretation of the meaning): 

“So woe unto those performers of
Salaah (prayers) (hypocrites),

5. Those who delay their Salaah
(prayer from their stated fixed times)”

[al-Maa’oon 107:4-5] 

Ibn Katheer said: 

It
was narrated from Ibn Mas’ood that it was said to him that Allaah mentions
prayer a great deal in the Qur’aan: “Those who
delay their Salaah (prayer from their stated fixed times)” [al-Maa’oon
107:5] and “Those who remain
constant in their Salaah (prayers)” [al-Ma’aarij 70:23]
and “and they are constant in guarding their Salaah (prayers)”
[al-An’aam 6:92]. Ibn
Mas’ood said: (This means) offering prayers at the stated times. They said:
We thought that these verses referred to not praying at all. He said: That
is kufr. 

Al-Awzaa’i
said, quoting from Ibraaheem ibn Yazeed, that ‘Umar ibn ‘Abd al-‘Azeez
recited: “Then, there has succeeded them a
posterity who have given up As-Salaat (the prayers) [i.e. made their Salaat
(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] and have
followed lusts. So they will be thrown in Hell” [Maryam 19:59].
Then he said: “Their giving up their prayers does not mean that they do not
pray at all, rather it means that they have given up praying at the proper
times.” 

Tafseer Ibn Katheer,
3/128, 129. 

So it is not
permissible for you to delay your prayers from the proper time based on the
excuse of work. If you cannot pray on time at work, then you should leave
this job and look for another job which will not cause you to miss your
prayers. The wise Muslim should not expose himself to the threat of his Lord
and he should not sell his religious commitment for the sake of passing
worldly interests. 

And Allaah
knows best.